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Number - Scientific Notation

Grade 7IB

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

🔑Concepts

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

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

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).

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 5×1045 \times 10^{4}.

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 6×1046 \times 10^{-4}.

When multiplying numbers in scientific notation, multiply the coefficients and add the exponents using the index law 10m×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.

When dividing numbers in scientific notation, divide the coefficients and subtract the exponents using the index law 10m10n=10mn\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.

📐Formulae

General Form: a×10na \times 10^{n}, where 1a<101 \le a < 10 and nn is an integer

Multiplication Rule: (a×10m)×(b×10n)=(a×b)×10m+n(a \times 10^{m}) \times (b \times 10^{n}) = (a \times b) \times 10^{m+n}

Division Rule: (a×10m)÷(b×10n)=(a÷b)×10mn(a \times 10^{m}) \div (b \times 10^{n}) = (a \div b) \times 10^{m-n}

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

💡Examples

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 6-6.
  5. Final result: 4.2×1064.2 \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 (5×104)×(4×103)(5 \times 10^{4}) \times (4 \times 10^{3}) and provide the answer in scientific notation.

Solution:

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