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Number - Scientific Notation

Grade 7IB

Review the key concepts, formulae, and examples before starting your quiz.

๐Ÿ”‘Concepts

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Scientific notation is a method of writing very large or very small numbers using powers of 10 in the format aร—10na \times 10^{n}. Visually, this simplifies long strings of zeros into a compact form comprising a coefficient and a power of ten.

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The coefficient, represented by aa, must be a number such that 1โ‰คa<101 \le a < 10. Visually, this means there should be exactly one non-zero digit to the left of the decimal point (e.g., 3.5ร—1023.5 \times 10^{2} is correct, but 35ร—10135 \times 10^{1} is not).

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The exponent nn represents the number of places the decimal point has moved and must be an integer. Visually, a positive exponent indicates a large number (greater than 1010), while a negative exponent indicates a small decimal (between 00 and 11).

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To convert a large number like 50,00050,000 to scientific notation, imagine the decimal at the end and move it to the left until only one non-zero digit remains on the left. Visually, the number of 'jumps' the decimal makes determines the positive exponent. For 50,00050,000, we jump 44 places to get 5ร—1045 \times 10^{4}.

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To convert a small decimal like 0.00060.0006 to scientific notation, move the decimal to the right until it is behind the first non-zero digit. Visually, the number of rightward jumps determines the negative exponent. For 0.00060.0006, moving 44 places right results in 6ร—10โˆ’46 \times 10^{-4}.

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When multiplying numbers in scientific notation, multiply the coefficients and add the exponents using the index law 10mร—10n=10m+n10^{m} \times 10^{n} = 10^{m+n}. Visually, you are treating the decimal parts and the power parts as separate groups before combining them.

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When dividing numbers in scientific notation, divide the coefficients and subtract the exponents using the index law 10m10n=10mโˆ’n\frac{10^{m}}{10^{n}} = 10^{m-n}. If the resulting coefficient is not between 11 and 1010, you must shift the decimal and adjust the exponent to maintain standard form.

๐Ÿ“Formulae

General Form: aร—10na \times 10^{n}, where 1โ‰คa<101 \le a < 10 and nn is an integer

Multiplication Rule: (aร—10m)ร—(bร—10n)=(aร—b)ร—10m+n(a \times 10^{m}) \times (b \times 10^{n}) = (a \times b) \times 10^{m+n}

Division Rule: (aร—10m)รท(bร—10n)=(aรทb)ร—10mโˆ’n(a \times 10^{m}) \div (b \times 10^{n}) = (a \div b) \times 10^{m-n}

Negative Power: 10โˆ’n=110n10^{-n} = \frac{1}{10^{n}}

๐Ÿ’กExamples

Problem 1:

Convert 0.00000420.0000042 into scientific notation.

Solution:

  1. Identify the first non-zero digit, which is 44.
  2. Move the decimal point from its original position to the space between the 44 and the 22.
  3. Count the decimal places moved: it moves 66 places to the right.
  4. Because the decimal moved right (representing a value less than 11), the exponent is โˆ’6-6.
  5. Final result: 4.2ร—10โˆ’64.2 \times 10^{-6}.

Explanation:

To write a small number in scientific notation, we shift the decimal until the coefficient is between 11 and 1010, using the count of jumps as a negative exponent.

Problem 2:

Calculate (5ร—104)ร—(4ร—103)(5 \times 10^{4}) \times (4 \times 10^{3}) and provide the answer in scientific notation.

Solution:

  1. Multiply the coefficients: 5ร—4=205 \times 4 = 20.
  2. Add the exponents of the powers of ten: 104+3=10710^{4+3} = 10^{7}.
  3. Combine them: 20ร—10720 \times 10^{7}.
  4. Adjust the coefficient to be between 11 and 1010: 20=2.0ร—10120 = 2.0 \times 10^{1}.
  5. Apply the extra power to the total: 2.0ร—101ร—107=2.0ร—1082.0 \times 10^{1} \times 10^{7} = 2.0 \times 10^{8}.

Explanation:

First multiply the numbers and add the powers. Since 2020 is not a valid coefficient for scientific notation, we convert it to 2.02.0 and increase the exponent by 11 to compensate.