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GMAT Online Course: Scientific Notation Simplified

  • Writer: Goalisb
    Goalisb
  • 23 minutes ago
  • 19 min read

Scientific Notation Simplified: Your GMAT Guide to Big and Small Numbers


Ever seen numbers like 300,000,000 (speed of light) or 0.0000000001 (size of an atom) and wondered how to handle them efficiently? That's where scientific notation comes in! It's a compact way to express very large or very small numbers, and it's a concept the GMAT expects you to understand.


GMAT Online Course: Scientific Notation Simplified

What is Scientific Notation?

Scientific notation expresses a number as a product of two parts:

  1. A coefficient: A number greater than or equal to 1 and less than 10 (i.e., 1 <= a < 10). This means it has only one non-zero digit to the left of the decimal point.

  2. A power of 10: 10^n, where n is an integer (positive for large numbers, negative for small numbers).

Format: a * 10^n

Converting Standard Notation to Scientific Notation

The key is to move the decimal point until you have only one non-zero digit to its left.

  • For Large Numbers (n will be positive):

    • Rule: Move the decimal point to the left until the number is between 1 and 10. The number of places you moved is n.

    • Example: Convert 345,000,000 to scientific notation.

      1. The decimal point is initially at the end: 345,000,000.

      2. Move it left until it's after the 3: 3.45000000

      3. Count the moves: 8 places.

      4. So, n = 8.

      5. Result: 3.45 * 10^8

  • For Small Numbers (n will be negative):

    • Rule: Move the decimal point to the right until the number is between 1 and 10. The number of places you moved is n, and it will be negative.

    • Example: Convert 0.0000078 to scientific notation.

      1. The decimal point is at the beginning: 0.0000078

      2. Move it right until it's after the 7: 000007.8 (effectively 7.8)

      3. Count the moves: 6 places.

      4. So, n = -6.

      5. Result: 7.8 * 10^-6

Converting Scientific Notation to Standard Notation

This is essentially "undoing" the previous process based on the exponent n.

  • If n is positive:

    • Rule: Move the decimal point to the right n times. Add trailing zeros as needed.

    • Example: Convert 1.23 * 10^5 to standard notation.

      1. Start with 1.23

      2. n = 5, so move decimal 5 places right.

      3. 1.23 -> 12.3 (1 move) -> 123. (2 moves) -> 1230. (3 moves) -> 12300. (4 moves) -> 123000. (5 moves)

      4. Result: 123,000

  • If n is negative:

    • Rule: Move the decimal point to the left |n| (absolute value of n) times. Add leading zeros as needed.

    • Example: Convert 9.0 * 10^-4 to standard notation.

      1. Start with 9.0

      2. n = -4, so move decimal 4 places left.

      3. 9.0 -> .90 (1 move) -> .090 (2 moves) -> .0090 (3 moves) -> .00090 (4 moves)

      4. Result: 0.0009 (trailing zeros can be dropped if not indicating precision).

GMAT Relevance

Scientific notation helps simplify calculations with very large or small numbers on the GMAT, especially in Problem Solving questions involving rates, distances, or probabilities. It also directly tests your understanding of decimal place values and exponent rules. Master these conversions to boost your efficiency!

Version 2: Self-Paced Course - "Lesson 4.2: Scientific Notation – Mastering the Language of Extremes"

Welcome to Lesson 4.2 of Module 4! In our previous lesson, we meticulously deconstructed the foundational concept of decimal place value. Now, we build upon that understanding to introduce Scientific Notation – an incredibly powerful and elegant tool for representing numbers that are either extraordinarily large or infinitesimally small. While such extreme numbers might seem confined to advanced science, they frequently appear in various forms on the GMAT, particularly in Data Interpretation, problem-solving scenarios involving scales (e.g., population, astronomical distances, microscopic sizes), and questions testing your proficiency with exponents and decimals.

This lesson will provide an exhaustive exploration of scientific notation. We will rigorously define its standard form, precisely outlining the strict rules that govern its structure. You will learn, step-by-step, the methodical process of converting numbers from their everyday "standard notation" into scientific notation, distinguishing between the handling of large and small values. Conversely, we will then thoroughly reverse the process, demonstrating how to transform scientific notation back into standard decimal form, always emphasizing the direct relationship between the exponent of 10 and the movement of the decimal point. By the end of this lesson, you will not only be proficient in these conversions but also appreciate the immense practical advantages that scientific notation offers for simplifying complex calculations and enhancing clarity.

I. What is Scientific Notation? Its Purpose and Standard Form

Scientific notation is essentially a universal shorthand system for expressing numbers that are inconveniently cumbersome to write out in their full, standard decimal form (i.e., numbers with many zeros before or after the decimal point). Its primary purpose is to simplify communication, standardize representation, and facilitate calculations involving these extreme magnitudes.

  • The Problem It Solves:

    • Imagine writing the number of atoms in a gram of hydrogen: 602,200,000,000,000,000,000,000. This is lengthy, prone to errors (missing or adding a zero), and hard to compare quickly.

    • Imagine writing the charge of an electron: 0.0000000000000000001602 Coulombs. Equally unwieldy.

    • Scientific notation provides a compact and unambiguous way to write such numbers.

  • The Standard Form: The Blueprint of Scientific Notation

    A number expressed in scientific notation always adheres to a very specific, strict format:

    a * 10^n

    Let's break down each component with meticulous detail:

    1. a (The Coefficient / Significand):

      • This is the numerical part of the scientific notation.

      • Crucial Rule: The absolute value of a must be greater than or equal to 1, and strictly less than 10. That is, 1 <= |a| < 10.

      • Implication: This means the coefficient a will always have exactly one non-zero digit to the left of the decimal point.

        • Valid coefficients: 1.0, 3.14, 9.99, -2.5

        • Invalid coefficients: 0.5 (less than 1), 10.0 (equal to 10), 12.3 (greater than 10)

      • Sign: The sign of the coefficient a (+ or -) determines the sign of the overall number. If a is positive, the number is positive. If a is negative, the number is negative.

    2. 10 (The Base):

      • This is always the number 10, as our number system is base-10. This is fixed.

    3. n (The Exponent / Power):

      • This is an integer that indicates how many places the decimal point has been moved.

      • Crucial Rule: n must be an integer (can be positive, negative, or zero).

      • Sign of n:

        • If n is a positive integer (n > 0), it means the original number was a large number (a value of 10 or greater). The decimal point was conceptually moved to the left to get to the a part.

        • If n is a negative integer (n < 0), it means the original number was a small number (a value between 0 and 1). The decimal point was conceptually moved to the right to get to the a part.

        • If n is zero (n = 0), it means the original number was already between 1 and 10 (or -1 and -10). For example, 5.7 in scientific notation is 5.7 * 10^0.

II. Converting Standard Notation to Scientific Notation: A Meticulous Process

This conversion requires careful, step-by-step manipulation of the decimal point and a precise count of its movements.

  • Case 1: Converting a Large Number (Original value > 10)

    When the absolute value of the original number is 10 or greater, the exponent n in 10^n will always be a positive integer.

    • Rule: Move the decimal point to the left until there is only one non-zero digit remaining to its left. The number of places you moved the decimal point will be the value of n.

    • Detailed Example 1: Convert 231,000 to scientific notation.

      • Step 1: Locate the Implied Decimal Point. For a whole number, the decimal point is implicitly at the very end: 231,000.

      • Step 2: Determine the Target Position for the Decimal Point. To form a coefficient a where 1 <= a < 10, the decimal point must be placed immediately after the first non-zero digit. In 231,000, the first non-zero digit from the left is 2. So, the target position is 2.31.

      • Step 3: Move the Decimal Point and Count the Places.

        • Start at 231,000.

        • Move 1 place left: 23,100.0

        • Move 2 places left: 2,310.00

        • Move 3 places left: 231.000

        • Move 4 places left: 23.1000

        • Move 5 places left: 2.31000

        • We moved the decimal point a total of 5 places to the left.

      • Step 4: Determine the Exponent n. Since we moved the decimal point 5 places to the left (making the number smaller to fit the 1 <= a < 10 rule), the exponent n will be positive 5. n = 5.

      • Step 5: Form the Scientific Notation. Combine the coefficient a (from Step 2, dropping unnecessary trailing zeros) and the power of 10 (10^n from Step 4).

        • Coefficient a = 2.31

        • Exponent n = 5

        • Result: 2.31 * 10^5

      • Self-Check: 2.31 10^5 = 2.31 100,000 = 231,000. (Matches original).

    • Detailed Example 2: Convert 87,654,321 to scientific notation.

      • Step 1: Implied decimal point: 87,654,321.

      • Step 2: Target a: 8.7654321.

      • Step 3: Count moves to the left. From 87,654,321. to 8.7654321:

        • Move past 1 (1st move)

        • Move past 2 (2nd move)

        • Move past 3 (3rd move)

        • Move past 4 (4th move)

        • Move past 5 (5th move)

        • Move past 6 (6th move)

        • Move past 7 (7th move)

        • Total moves: 7 places to the left.

      • Step 4: Exponent n = 7.

      • Step 5: Form notation: 8.7654321 * 10^7.

  • Case 2: Converting a Small Number (Original value between 0 and 1)

    When the absolute value of the original number is between 0 and 1, the exponent n in 10^n will always be a negative integer.

    • Rule: Move the decimal point to the right until there is only one non-zero digit remaining to its left. The number of places you moved the decimal point will be the value of |n|, and n will be negative.

    • Detailed Example 1: Convert 0.00000789 to scientific notation.

      • Step 1: Locate the Decimal Point. The decimal point is at the beginning: 0.00000789

      • Step 2: Determine the Target Position for the Decimal Point. To form a coefficient a where 1 <= a < 10, the decimal point must be placed immediately after the first non-zero digit encountered from the left. In 0.00000789, the first non-zero digit is 7. So, the target position is 7.89.

      • Step 3: Move the Decimal Point and Count the Places.

        • Start at 0.00000789

        • Move 1 place right: 00.0000789 (conceptually 0.0000789)

        • Move 2 places right: 000.000789

        • Move 3 places right: 0000.00789

        • Move 4 places right: 00000.0789

        • Move 5 places right: 000000.789

        • Move 6 places right: 0000007.89 (effectively 7.89)

        • We moved the decimal point a total of 6 places to the right.

      • Step 4: Determine the Exponent n. Since we moved the decimal point 6 places to the right (making the number larger to fit the 1 <= a < 10 rule), the exponent n will be negative 6. n = -6.

      • Step 5: Form the Scientific Notation. Combine the coefficient a (from Step 2, dropping leading zeros) and the power of 10 (10^n from Step 4).

        • Coefficient a = 7.89

        • Exponent n = -6

        • Result: 7.89 * 10^-6

      • Self-Check: 7.89 10^-6 = 7.89 (1/1000000) = 7.89 / 1,000,000 = 0.00000789. (Matches original).

    • Detailed Example 2: Convert 0.0004 to scientific notation.

      • Step 1: Decimal point: 0.0004

      • Step 2: Target a: 4. (or 4.0 for clarity).

      • Step 3: Count moves to the right. From 0.0004 to 4.0:

        • Move past first 0 (1st move)

        • Move past second 0 (2nd move)

        • Move past third 0 (3rd move)

        • Move past 4 (4th move)

        • Total moves: 4 places to the right.

      • Step 4: Exponent n = -4.

      • Step 5: Form notation: 4.0 * 10^-4.

III. Converting Scientific Notation to Standard Notation: Reversing the Process

This conversion involves "undoing" the decimal point movement based on the sign and magnitude of the exponent n.

  • Case 1: n is a Positive Integer (Original number was Large)

    If the exponent n is positive, it signifies that the original number was a large number. To convert back, you must make the coefficient a larger by moving the decimal point to the right.

    • Rule: Move the decimal point to the right n times. Add trailing zeros as placeholders if you run out of digits in the coefficient.

    • Detailed Example 1: Convert 6.022 * 10^23 to standard notation.

      • Step 1: Identify the Coefficient and Exponent.

        • Coefficient a = 6.022

        • Exponent n = 23

      • Step 2: Determine the Direction and Number of Decimal Moves. Since n = 23 (positive), we move the decimal point 23 places to the right.

      • Step 3: Execute the Decimal Point Movement.

        • Start with 6.022

        • Move 1 place right: 60.22

        • Move 2 places right: 602.2

        • Move 3 places right: 6022.

        • At this point, we've moved 3 places, and we have 23 - 3 = 20 more places to move. Since there are no more digits to move past, we fill the remaining 20 places with zeros.

        • So, we add 20 zeros after the 2.

      • Step 4: Form the Standard Notation.

        • 6022 followed by 20 zeros.

        • 602,200,000,000,000,000,000,000

      • Self-Check: This number is indeed very large, consistent with a positive exponent of 23.

    • Detailed Example 2: Convert 3.14 * 10^3 to standard notation.

      • Step 1: a = 3.14, n = 3.

      • Step 2: Move decimal 3 places to the right.

      • Step 3:

        • 3.14

        • 31.4 (1 move)

        • 314. (2 moves)

        • 3140. (3 moves - added one zero)

      • Step 4: 3,140.

  • Case 2: n is a Negative Integer (Original number was Small)

    If the exponent n is negative, it signifies that the original number was a small number (between 0 and 1, or between -1 and 0). To convert back, you must make the coefficient a smaller by moving the decimal point to the left.

    • Rule: Move the decimal point to the left |n| (the absolute value of n) times. Add leading zeros as placeholders if you run out of digits in the coefficient.

    • Detailed Example 1: Convert 1.602 * 10^-19 to standard notation.

      • Step 1: Identify the Coefficient and Exponent.

        • Coefficient a = 1.602

        • Exponent n = -19

      • Step 2: Determine the Direction and Number of Decimal Moves. Since n = -19 (negative), we move the decimal point |-19| = 19 places to the left.

      • Step 3: Execute the Decimal Point Movement.

        • Start with 1.602

        • Move 1 place left: .1602

        • We have moved 1 place. We need to move 19 - 1 = 18 more places. Since there are no more digits to move past on the left, we add 18 leading zeros between the decimal point and the 1.

        • 0. (decimal point) 000000000000000000 (18 zeros) 1602

      • Step 4: Form the Standard Notation.

        • 0.0000000000000000001602

      • Self-Check: This number is indeed very small, consistent with a negative exponent of -19.

    • Detailed Example 2: Convert 8.5 * 10^-3 to standard notation.

      • Step 1: a = 8.5, n = -3.

      • Step 2: Move decimal |-3| = 3 places to the left.

      • Step 3:

        • 8.5

        • .85 (1 move)

        • .085 (2 moves - added one leading zero)

        • .0085 (3 moves - added another leading zero)

      • Step 4: 0.0085.

IV. Why Scientific Notation is Indispensable for the GMAT (And Beyond)

Beyond merely being a compact way to write numbers, scientific notation offers profound advantages that are implicitly and explicitly tested on the GMAT:

  • Simplified Calculations with Extremes: When multiplying or dividing very large or very small numbers, scientific notation significantly simplifies the process by separating the decimal arithmetic from the exponent arithmetic.

    • Example: Instead of (600,000 0.00002), you can do (6 10^5) (2 10^-5) = (6*2) (10^5 10^-5) = 12 10^0 = 12 1 = 12. This is much easier!

    • This leverages the exponent rules you learned in Module 3 (e.g., 10^a * 10^b = 10^(a+b)).

  • Magnitude Comparison: It allows for quick and accurate comparison of the relative sizes of numbers, especially when comparing numbers of vastly different scales. The exponent n immediately tells you the order of magnitude. 10^5 is clearly much larger than 10^-2.

  • GMAT Problem Solving Efficiency: Problems involving rates, distances, populations, or scientific data often include very large or very small numbers. Scientific notation provides the most efficient way to represent and manipulate these numbers to arrive at a solution.

  • Decimal Place Value Reinforcement: The process of converting between standard and scientific notation is a direct application and reinforcement of your understanding of decimal place values, requiring you to count positions accurately.

V. Common Pitfalls to Avoid in Scientific Notation (Detailed Traps & Solutions)

Successfully navigating scientific notation problems on the GMAT requires vigilance against several common conceptual and procedural errors.

  1. Incorrect Coefficient (a):

    • The Trap: Failing to ensure that the coefficient a strictly adheres to the rule 1 <= |a| < 10. Common errors include 23.1 10^4 or 0.231 10^6.

    • The Reality & Mitigation: The coefficient must have exactly one non-zero digit to the left of the decimal point.

      • 23.1 10^4 is incorrect. To fix: Move decimal in 23.1 one place left to get 2.31. Since you made 23.1 smaller by a factor of 10 (10^1), you must compensate by increasing the exponent by 1: 2.31 10^(4+1) = 2.31 * 10^5.

      • 0.231 10^6 is incorrect. To fix: Move decimal in 0.231 one place right to get 2.31. Since you made 0.231 larger by a factor of 10 (10^1), you must compensate by decreasing the exponent by 1: 2.31 10^(6-1) = 2.31 * 10^5.

    • Strategy: Always perform a quick check of your coefficient after conversion: Is it between 1 and 10? If not, adjust a and simultaneously adjust n in the opposite direction.

  2. Incorrect Sign of the Exponent (n):

    • The Trap: Confusing when n should be positive versus negative, especially when converting from standard to scientific notation. A large number might incorrectly get a negative exponent, or a small number a positive one.

    • The Reality & Mitigation:

      • Think "Large Number" (Positive n): If the original number is larger than 10 (e.g., 5,000), you moved the decimal to the left to make the coefficient smaller (5.0). To compensate for making it smaller, the exponent n must be positive to "magnify" it back to its original large size.

      • Think "Small Number" (Negative n): If the original number is between 0 and 1 (e.g., 0.005), you moved the decimal to the right to make the coefficient larger (5.0). To compensate for making it larger, the exponent n must be negative to "shrink" it back to its original small size.

    • Strategy: After determining n, always perform a quick mental check: "Does a 10^n approximately equal the original number?" If 5 10^3 = 5000 (correct) but 5 * 10^-3 = 0.005 (incorrect for 5000), you've got the wrong sign.

  3. Miscounting Decimal Places:

    • The Trap: Off-by-one errors when counting how many places the decimal point moved. This is particularly common with numbers containing many zeros.

    • The Reality & Mitigation: Every single place the decimal point moves counts as one unit for n.

      • When moving right, count the number of places between the original decimal point and its new position.

      • When moving left, count the number of places between the original decimal point and its new position.

    • Strategy: For critical calculations, physically draw loops or arrows on your scratchpad to indicate each decimal place jump you count. For example, 0.000 (arrow over first 0) 0 (arrow over second 0) 0 (arrow over third 0) 789 (arrow after 7). This visual aid reduces miscounts.

  4. Forgetting to Apply Exponent Rules in Calculations:

    • The Trap: When multiplying or dividing numbers in scientific notation, forgetting that the exponent rules for 10^n apply (e.g., adding exponents for multiplication, subtracting for division).

    • The Reality & Mitigation:

      • (A 10^x) (B 10^y) = (A B) * 10^(x+y)

      • (A 10^x) / (B 10^y) = (A / B) * 10^(x-y)

    • Strategy: Always treat the powers of 10 as separate exponential terms and apply the exponent rules learned in Module 3. Remember that the coefficients (A and B) are multiplied or divided normally.

VI. Interactive Check Your Understanding: (Step-by-Step Guidance)

  1. Convert 93,000,000 (approximate distance to the sun in miles) to scientific notation.

    • Thought Process: This is a large number, so the exponent n will be positive. We need to move the decimal point to the left until only one non-zero digit (9) is before it.

    • Steps:

      • Original number with implied decimal: 93,000,000.

      • Target coefficient: 9.3

      • Count moves left: From 93,000,000. to 9.3: 7 places.

      • Since moved left, n = 7.

    • Answer: 9.3 * 10^7.

  2. Convert 0.000000001 (1 nanometer) to scientific notation.

    • Thought Process: This is a very small number, so the exponent n will be negative. We need to move the decimal point to the right until only one non-zero digit (1) is before it.

    • Steps:

      • Original number: 0.000000001

      • Target coefficient: 1.0

      • Count moves right: From 0.000000001 to 1.0: 9 places.

      • Since moved right, n = -9.

    • Answer: 1.0 * 10^-9.

  3. Convert 4.7 * 10^6 to standard decimal notation.

    • Thought Process: The exponent n = 6 is positive, so the original number was large. We need to make 4.7 larger by moving the decimal point to the right.

    • Steps:

      • Start with 4.7.

      • Move decimal 6 places to the right.

        • 4.7 (initial)

        • 47. (1 move)

        • 470. (2 moves, added 1 zero)

        • 4700. (3 moves, added 2 zeros)

        • 47000. (4 moves, added 3 zeros)

        • 470000. (5 moves, added 4 zeros)

        • 4700000. (6 moves, added 5 zeros)

    • Answer: 4,700,000.

  4. Convert 2.5 * 10^-4 to standard decimal notation.

    • Thought Process: The exponent n = -4 is negative, so the original number was small. We need to make 2.5 smaller by moving the decimal point to the left.

    • Steps:

      • Start with 2.5.

      • Move decimal |-4| = 4 places to the left.

        • 2.5 (initial)

        • .25 (1 move)

        • .025 (2 moves, added 1 leading zero)

        • .0025 (3 moves, added 2 leading zeros)

        • .00025 (4 moves, added 3 leading zeros)

    • Answer: 0.00025.

VII. Practice Questions: (With Exhaustive Step-by-Step Solutions)

  1. Express 54,000,000,000 in scientific notation.

    a) 5.4 * 10^10

    b) 54 * 10^9

    c) 5.4 * 10^11

    d) 0.54 * 10^11

  2. Convert 7.12 * 10^-7 to standard decimal notation.

    a) 0.000000712

    b) 0.00000712

    c) 71,200,000

    d) 0.0000000712

  3. If X = 0.0000003 and Y = 90,000,000, what is the value of X * Y in scientific notation?

    a) 2.7 * 10^1

    b) 2.7 * 10^0

    c) 2.7 * 10^-1

    d) 2.7 * 10^2

  4. A bacterial colony grows from 5 10^3 cells to 5 10^7 cells. By what factor did the colony grow? (Express in standard notation).

Exhaustive Step-by-Step Solutions to Practice Questions:

  1. Express 54,000,000,000 in scientific notation.

    • Goal: Convert a large standard number to a * 10^n format where 1 <= a < 10.

    • Step 1: Identify the implied decimal point. For 54,000,000,000, the decimal point is at the very end: 54,000,000,000.

    • Step 2: Determine the desired position for the decimal point for the coefficient a. The first non-zero digit is 5. So, the decimal point must be placed after the 5 to create 5.4.

    • Step 3: Count the number of places the decimal point must move to the left to reach 5.4.

      • Starting from 54,000,000,000.:

      • Move past the first 0 (1st move)

      • Move past the second 0 (2nd move)

      • ... (continue moving past all 0s) ...

      • Move past the ninth 0 (9th move)

      • Move past the 4 (10th move)

      • The decimal point moved 10 places to the left.

    • Step 4: Determine the exponent n. Since the decimal point moved 10 places to the left (making the number smaller), the exponent n must be positive 10. So, n = 10.

    • Step 5: Form the scientific notation. The coefficient a is 5.4 (dropping the trailing zeros that are no longer significant after the new decimal point), and n is 10. 5.4 * 10^10.

    • Final Answer: a) 5.4 * 10^10.

  2. Convert 7.12 * 10^-7 to standard decimal notation.

    • Goal: Convert a number from scientific notation (a * 10^n) back to its full decimal form.

    • Step 1: Identify the coefficient (a) and the exponent (n).

      • a = 7.12

      • n = -7

    • Step 2: Determine the direction and number of decimal point moves. Since n = -7 (a negative exponent), the original number was very small. To make 7.12 smaller, we must move the decimal point to the left. The number of moves is the absolute value of n, which is 7 places.

    • Step 3: Execute the decimal point movement.

      • Start with 7.12.

      • Move 1 place left: .712 (the decimal is now before the 7)

      • We need to move 7 - 1 = 6 more places. For these 6 additional moves to the left, we will add leading zeros between the decimal point and the 7.

      • So, we'll have 0. followed by 6 zeros, then 712.

      • 0.000000712

    • Step 4: Write the final standard decimal notation.

    • Final Answer: a) 0.000000712.

  3. If X = 0.0000003 and Y = 90,000,000, what is the value of X * Y in scientific notation?

    • Goal: Multiply two numbers given in standard notation, and express the product in scientific notation. This is best done by converting to scientific notation first.

    • Step 1: Convert X to scientific notation.

      • X = 0.0000003. This is a small number, so n will be negative.

      • Move decimal right until after the 3: 3.

      • Count moves: 0.0 (1) 0 (2) 0 (3) 0 (4) 0 (5) 0 (6) 3. (7 moves).

      • So, X = 3.0 * 10^-7.

    • Step 2: Convert Y to scientific notation.

      • Y = 90,000,000. This is a large number, so n will be positive.

      • Move decimal left until after the 9: 9.

      • Count moves: 90,000,000. to 9.0 is 7 places.

      • So, Y = 9.0 * 10^7.

    • Step 3: Multiply X * Y using scientific notation.

      • X Y = (3.0 10^-7) (9.0 10^7)

      • Rule: Multiply the coefficients together, and add the exponents of the powers of 10.

        • Multiply coefficients: 3.0 * 9.0 = 27.0.

        • Add exponents: 10^-7 * 10^7 = 10^(-7 + 7) = 10^0.

      • So, X Y = 27.0 10^0.

    • Step 4: Ensure the final product is in proper scientific notation.

      • The coefficient 27.0 is not between 1 and 10 (27.0 >= 10). We need to adjust it.

      • Move the decimal point in 27.0 one place to the left to get 2.7.

      • Since we made the coefficient 27.0 smaller by a factor of 10 (moved decimal left 1 place), we must compensate by increasing the exponent of 10 by 1.

      • Original exponent was 0. New exponent is 0 + 1 = 1.

      • So, 27.0 10^0 becomes 2.7 10^1.

    • Final Answer: a) 2.7 * 10^1.

  4. A bacterial colony grows from 5 10^3 cells to 5 10^7 cells. By what factor did the colony grow? (Express in standard notation).

    • Goal: Find the factor of growth, which means dividing the final size by the initial size. Then, convert the result to standard notation.

    • Step 1: Set up the division for the growth factor.

      • Growth Factor = (Final Size) / (Initial Size)

      • Growth Factor = (5 10^7) / (5 10^3)

    • Step 2: Perform the division using exponent rules.

      • Rule: Divide the coefficients, and subtract the exponents of the powers of 10.

        • Divide coefficients: 5 / 5 = 1.

        • Subtract exponents: 10^7 / 10^3 = 10^(7 - 3) = 10^4.

      • So, the growth factor in scientific notation is 1 * 10^4.

    • Step 3: Convert the result to standard notation.

      • The exponent is 4 (positive), so move the decimal point in 1.0 4 places to the right.

      • 1.0 -> 10. (1) -> 100. (2) -> 1000. (3) -> 10000. (4)

    • Final Answer: The colony grew by a factor of 10,000.

VIII. Self-Assessment Checklist for Lesson 4.2 Mastery

Before moving forward, utilize this checklist to confirm your comprehensive understanding of Scientific Notation. If you can answer "Yes" to all, you are well-prepared.

  • Can you define scientific notation and explain the purpose of its two main parts (a and 10^n)?

    • [ ] Yes [ ] No

  • Do you know the strict rule for the coefficient a (1 <= |a| < 10) and why it's important?

    • [ ] Yes [ ] No

  • Can you confidently convert any large number from standard notation to scientific notation, determining the correct positive exponent?

    • [ ] Yes [ ] No

  • Can you confidently convert any small number (between 0 and 1) from standard notation to scientific notation, determining the correct negative exponent?

    • [ ] Yes [ ] No

  • Can you convert any number in scientific notation with a positive exponent back to standard decimal notation?

    • [ ] Yes [ ] No

  • Can you convert any number in scientific notation with a negative exponent back to standard decimal notation?

    • [ ] Yes [ ] No

  • Do you understand how multiplication and division of numbers in scientific notation are performed by operating on coefficients and exponents separately?

    • [ ] Yes [ ] No

  • Are you aware of and can you avoid the common pitfalls (incorrect a, wrong exponent sign, miscounting places)?

    • [ ] Yes [ ] No

 
 
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