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ESO Y4A · Mathematics
Numbers · Powers and roots

Scientific notation

The mass of the Earth is $5\,970\,000\,000\,000\,000\,000\,000\,000$ kg. The mass of an oxygen atom is $0{,}0000000000000000000000266$ g. No scientist writes this with all those zeros: they use powers of 10. It is the standard language for working with astronomical or subatomic scales without losing count of the digits.

Before you start, make sure you know: Scientific notation (3rd ESO)
Before you start, make sure you know: Operations with powers (3rd ESO)

What scientific notation is

Travel across the scales of the universe, from the atom to the galaxy, all on the same line:

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Express the following integers and terminating decimals in standard form: a) $450\,000\,000$ b) $32\,500$ c) $8\,400\,000\,000\,000$

Express the following integers and terminating decimals in standard form:

  1. a) $450\,000\,000$
  2. b) $32\,500$
  3. c) $8\,400\,000\,000\,000$
Solve
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Express the following small decimal numbers in standard form: a) $0,0000045$ b) $0,00000000128$ c) $0,003$

Express the following small decimal numbers in standard form:

  1. a) $0,0000045$
  2. b) $0,00000000128$
  3. c) $0,003$
Solve

Converting between scientific notation and decimal form

The exponent counts how many places the decimal point moves.

Diagram of the movement of the decimal point when writing a number greater than 10 with a positive exponent and a number less than 1 with a negative exponent. 1 4 9 6 0 0 0 0 0 , 8 places to the left → 10⁸ = 1,496 · 10⁸ 0 , 0 0 0 0 0 0 1 2 7 places to the right → 10⁻⁷ = 1,2 · 10⁻⁷
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Write out in full the following numbers given in standard form: a) $3,14 \cdot 10^6$ b) $8,05 \cdot 10^9$ c) $1,002 \cdot 10^4$

Write out in full the following numbers given in standard form:

  1. a) $3,14 \cdot 10^6$
  2. b) $8,05 \cdot 10^9$
  3. c) $1,002 \cdot 10^4$
Solve
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Write the following numbers given in standard form in decimal form: a) $5,2 \cdot 10^{-5}$ b) $1,07 \cdot 10^{-8}$ c) $9,9 \cdot 10^{-3}$

Write the following numbers given in standard form in decimal form:

  1. a) $5,2 \cdot 10^{-5}$
  2. b) $1,07 \cdot 10^{-8}$
  3. c) $9,9 \cdot 10^{-3}$
Solve

Comparing and ordering

The exponent comes first. The mantissas are compared only if the exponents are the same.

Flowchart for comparing numbers in scientific notation by first checking the exponents and, if they are the same, the mantissas. logarithmic scale 10⁵ 10⁶ 10⁷ 10⁸ 4,5·10⁵ 3,2·10⁶ each mark is ×10 the previous one
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Order the following numbers from smallest to largest, having first expressed them in standard form (with a single non-zero digit before the decimal point):…

Order the following numbers from smallest to largest, having first expressed them in standard form (with a single non-zero digit before the decimal point):

$A = 0,0034 \cdot 10^8$

$B = 450 \cdot 10^3$

$C = 3,2 \cdot 10^5$

$D = 0,05 \cdot 10^7$

Solve

Operating in scientific notation

Step-by-step diagram of multiplication in scientific notation: multiplying the mantissas, adding the exponents and adjusting the final result. (6·10⁸) · (4·10⁻³) 6 · 4 · 10⁸ · 10⁻³ mantissas: are multiplied powers: exponents are added 24 · 10⁵ = 2,4 · 10⁶

Multiplying and dividing: the mantissas and the powers of 10 are dealt with separately, adding or subtracting the exponents; at the end, adjust the mantissa if it falls outside $[1, 10)$.

Adding and subtracting: the powers of 10 must be the same; if they are not, make them equal first.

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Carry out the following multiplications and give the answer in standard form: a) $(3 \cdot 10^4) \cdot (2 \cdot 10^5)$ b) $(4 \cdot 10^{-3}) \cdot (2 \cdot 10^8)$

Carry out the following multiplications and give the answer in standard form:

  1. a) $(3 \cdot 10^4) \cdot (2 \cdot 10^5)$
  2. b) $(4 \cdot 10^{-3}) \cdot (2 \cdot 10^8)$
Solve
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The mean distance from the Earth to the Sun is about $149\,600\,000$ km and the speed of light in a vacuum is approximately $300\,000$ km/s. Express both quantities in…

The mean distance from the Earth to the Sun is about $149\,600\,000$ km and the speed of light in a vacuum is approximately $300\,000$ km/s. Express both quantities in standard form and calculate how many seconds it takes for light from the Sun to reach the Earth.

Solve
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The law of universal gravitation states that the gravitational force between two masses $m_1$ and $m_2$ separated by a distance $d$ is…

The law of universal gravitation states that the gravitational force between two masses $m_1$ and $m_2$ separated by a distance $d$ is $F = G \cdot \frac{m_1 \cdot m_2}{d^2}$, where $G = 6,67 \cdot 10^{-11} \text{ N}\cdot\text{m}^2/\text{kg}^2$. Calculate the force of attraction between the Earth ($m_1 = 5,97 \cdot 10^{24}$ kg) and the Moon ($m_2 = 7,35 \cdot 10^{22}$ kg), given that the mean distance between their centres is $3,84 \cdot 10^8$ m. Give the answer in standard form to three significant figures.

Solve

Back to the beginning: The mass of the Earth in scientific notation is $5{,}97 \cdot 10^{24}$ kg and the mass of an oxygen atom is $2{,}66 \cdot 10^{-23}$ g.

Summary

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