Scientific Notation
The Sun is about $93{,}000{,}000$ miles from Earth. Light travels about $186{,}000$ miles every second. How long does sunlight take to reach us? You could count zeros all day, but scientists use powers of $10$ instead. This page shows you how, so you can work with giant and tiny numbers without losing a single digit.
What is scientific notation?
Every power of $10$ is a place-value jump: $10^3 = 1{,}000$, $10^6 = 1{,}000{,}000$. So we can write a huge number as "a small number times a power of $10$."
Explore the scales of the universe, from atoms to galaxies, on one number line where each tick is $10$ times the previous one:
Why the rule $1 \le a < 10$? It makes the notation unique. Without it, $45 \times 10^{3}$, $4.5 \times 10^{4}$ and $0.45 \times 10^{5}$ would all be "the same number" in different clothes. Scientific notation picks one standard way to write it.
Indicate which of the following numbers are not correctly written in scientific notation and write them correctly: a) $45,2 \cdot 10^3$ b) $0,8 \cdot 10^{-2}$ c)…
Indicate which of the following numbers are not correctly written in scientific notation and write them correctly:
- a) $45,2 \cdot 10^3$
- b) $0,8 \cdot 10^{-2}$
- c) $3,1 \cdot 10^5$
- d) $12 \cdot 10^{-4}$
Converting between scientific and standard form
The exponent tells you how many places the decimal point moves. Multiplying by $10^3$ shifts the point $3$ places right. Multiplying by $10^{-3} = \tfrac{1}{1{,}000}$ shifts it $3$ places left.
Write the following decimal numbers in scientific notation: a) $450 000 000$ b) $0,000000032$ c) $12 500$ d) $0,000105$
Write the following decimal numbers in scientific notation:
- a) $450 000 000$
- b) $0,000000032$
- c) $12 500$
- d) $0,000105$
Express the following numbers given in scientific notation in standard decimal form: a) $3,4 \cdot 10^5$ b) $1,89 \cdot 10^{-4}$ c) $7 \cdot 10^8$ d) $5,02 \cdot 10^{-6}$
Express the following numbers given in scientific notation in standard decimal form:
- a) $3,4 \cdot 10^5$
- b) $1,89 \cdot 10^{-4}$
- c) $7 \cdot 10^8$
- d) $5,02 \cdot 10^{-6}$
Comparing and ordering
Compare the exponents first. Only if the exponents are equal do you compare the coefficients.
Order of magnitude
The order of magnitude of a number is the power of $10$ nearest to it. It tells you "about how big" without the details. Look at the coefficient $a$ in $a \times 10^n$. The number sits between $10^n$ and $10^{n+1}$, and the halfway point between those two powers is $\dfrac{10^n + 10^{n+1}}{2} = 5.5 \times 10^n$. So:
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if $a < 5.5$, the number is closer to $10^n$, and the order of magnitude is $10^n$;
-
if $a \ge 5.5$, the number is closer to the next power, and the order of magnitude is $10^{n+1}$.
Many classes use "$a$ below $5$ rounds down, $a$ at least $5$ rounds up" as a quick shortcut. The two rules differ only for coefficients between $5$ and $5.5$.
For example, $3.2 \times 10^{8}$ has order of magnitude $10^{8}$. And $7.1 \times 10^{-3}$ is closer to $10 \times 10^{-3}$, so its order of magnitude is $10^{-2}$.
Order the following numbers written in scientific notation from least to greatest: $A = 3,2 \cdot 10^4$ $B = 4,1 \cdot 10^{-3}$ $C = 1,5 \cdot 10^4$…
Order the following numbers written in scientific notation from least to greatest:
$A = 3,2 \cdot 10^4$
$B = 4,1 \cdot 10^{-3}$
$C = 1,5 \cdot 10^4$
$D = 8,9 \cdot 10^{-4}$
$E = 2 \cdot 10^5$
Determine the order of magnitude (the nearest power of $10$) of the following quantities expressed in scientific notation: a) $4,8 \cdot 10^6$ b) $1,1 \cdot 10^{-5}$ c)…
Determine the order of magnitude (the nearest power of $10$) of the following quantities expressed in scientific notation:
- a) $4,8 \cdot 10^6$
- b) $1,1 \cdot 10^{-5}$
- c) $9,2 \cdot 10^{12}$
- d) $2,5 \cdot 10^{-8}$
Multiplying and dividing
Multiplication is commutative and associative, so you can regroup: multiply the coefficients together, and multiply the powers of $10$ together using the exponent rules ($10^m \cdot 10^n = 10^{m+n}$ and $\dfrac{10^m}{10^n} = 10^{m-n}$). At the end, check whether the coefficient is still between $1$ and $10$.
In the last step, $24 \times 10^5$ is not in scientific notation. Writing $24 = 2.4 \times 10$ gives $2.4 \times 10 \times 10^5 = 2.4 \times 10^6$. Every time the coefficient grows past $10$, the exponent goes up by one.
Perform the following multiplications by grouping the numbers and the powers of base $10$. Express the final result in scientific notation: a)…
Perform the following multiplications by grouping the numbers and the powers of base $10$. Express the final result in scientific notation:
- a) $(3 \cdot 10^4) \cdot (2 \cdot 10^5)$
- b) $(4 \cdot 10^{-3}) \cdot (2 \cdot 10^{-4})$
- c) $(5 \cdot 10^6) \cdot (3 \cdot 10^{-2})$
Carry out the following divisions and give the result in scientific notation: a) $(8 \cdot 10^7) : (2 \cdot 10^3)$ b) $(9 \cdot 10^{-4}) : (3 \cdot 10^{-2})$ c)…
Carry out the following divisions and give the result in scientific notation:
- a) $(8 \cdot 10^7) : (2 \cdot 10^3)$
- b) $(9 \cdot 10^{-4}) : (3 \cdot 10^{-2})$
- c) $(1,5 \cdot 10^5) : (3 \cdot 10^8)$
Solve the following combined operation respecting the order of operations and give the final result adjusted in scientific notation:…
Solve the following combined operation respecting the order of operations and give the final result adjusted in scientific notation:
$\frac{(4,2 \cdot 10^5) \cdot (2 \cdot 10^{-3})}{3 \cdot 10^4}$
Adding and subtracting
For adding and subtracting you cannot multiply the coefficients. You need equal powers of $10$, just like adding fractions needs a common denominator. Then add or subtract the coefficients and keep the power of $10$ unchanged. It works because of the distributive property: $4 \times 10^5 + 3 \times 10^5 = (4 + 3) \times 10^5$.
Calculate the following additions and subtractions that have the same exponent in the power of $10$: a) $4,2 \cdot 10^5 + 3,1 \cdot 10^5$ b)…
Calculate the following additions and subtractions that have the same exponent in the power of $10$:
- a) $4,2 \cdot 10^5 + 3,1 \cdot 10^5$
- b) $8,7 \cdot 10^{-3} - 2,5 \cdot 10^{-3}$
- c) $5,5 \cdot 10^8 + 4,5 \cdot 10^8$
Calculate the following additions and subtractions with different exponents, first adjusting the powers of $10$ so that they match. Express the result in scientific…
Calculate the following additions and subtractions with different exponents, first adjusting the powers of $10$ so that they match. Express the result in scientific notation:
- a) $3,5 \cdot 10^6 + 4,2 \cdot 10^5$
- b) $7,1 \cdot 10^{-4} - 5 \cdot 10^{-5}$
Carry out the following combined operation with additions and subtractions in the numerator and denominator. Express the final result strictly in scientific notation:…
Carry out the following combined operation with additions and subtractions in the numerator and denominator. Express the final result strictly in scientific notation:
$\frac{3,6 \cdot 10^{12} + 4,1 \cdot 10^{11}}{2 \cdot 10^{-3} - 5 \cdot 10^{-4}}$
Powers of numbers in scientific notation
Formulas like $E = \tfrac{1}{2}mv^2$, $V = \tfrac{4}{3}\pi R^3$ or $F = G\dfrac{m_1 m_2}{d^2}$ raise a number to a power. Two exponent rules do the job: $(ab)^k = a^k b^k$ and $(10^m)^k = 10^{mk}$. So
$$(a \times 10^{n})^{k} = a^{k} \times 10^{nk}.$$Raise the coefficient to the power, and multiply the exponent by $k$.
Powers also appear in growth. Suppose a video has $2 \times 10^{3}$ views and the count doubles every hour. After $6$ hours the views are $2 \times 10^{3} \cdot 2^{6}$. Since $2^{6} = 64$, that is $128 \times 10^{3} = 1.28 \times 10^{5}$. Try other bases and exponents to see how fast doubling grows:
In a microbiology experiment, a colony of bacteria initially contains $5 \cdot 10^4$ individuals and its population is observed to double every day. If the growth…
In a microbiology experiment, a colony of bacteria initially contains $5 \cdot 10^4$ individuals and its population is observed to double every day. If the growth follows the model $P = P_0 \cdot 2^t$ (where $t$ is the number of days), how many bacteria will there be after $10$ days? Express the final result in scientific notation. (Helpful fact: $2^{10} = 1024$).
Converting units inside formulas
Formulas and constants come with units attached. The gravitational constant $G$ uses kilograms and meters. A kinetic energy in joules (J) needs kilograms and meters per second. If a problem gives you miles, feet or pounds, convert every quantity first, then plug into the formula.
| To convert | Multiply by |
|---|---|
| miles → kilometers | $1.609$ |
| feet → meters | $0.3048$ |
| pounds → kilograms | $0.4536$ |
| grams → kilograms | $10^{-3}$ |
One more fact: $1\text{ J} = 1\text{ kg} \cdot \text{m}^2/\text{s}^2$. So if the mass is in kg and the speed is in m/s, the energy $\tfrac{1}{2}mv^2$ comes out directly in joules. In the same way, $1\text{ N} = 1\text{ kg} \cdot \text{m}/\text{s}^2$.
To make astronomical estimates, the Earth can be approximated as a perfect sphere with a radius of $R = 6,37 \cdot 10^3$ miles. Knowing that the volume of a sphere is…
To make astronomical estimates, the Earth can be approximated as a perfect sphere with a radius of $R = 6,37 \cdot 10^3$ miles. Knowing that the volume of a sphere is calculated using the formula $V = \frac{4}{3}\pi R^3$, calculate the volume of the Earth in $km^3$. Express the final result in scientific notation, rounding to two decimal places. (Use $\pi \approx 3,14$).
The kinetic energy ($E_c$) of a moving body is calculated with the expression $E_c = \frac{1}{2} m v^2$, where $m$ is the mass in lb and $v$ is the speed in ft/s.…
The kinetic energy ($E_c$) of a moving body is calculated with the expression $E_c = \frac{1}{2} m v^2$, where $m$ is the mass in lb and $v$ is the speed in ft/s. Calculate the kinetic energy of an asteroid of mass $m = 4,5 \cdot 10^{14}$ lb traveling through space at a speed of $v = 2 \cdot 10^4$ ft/s. Express the result in Joules (J) using scientific notation.
Newton's Law of Universal Gravitation states that the force of attraction between two bodies is given by $F = G \frac{m_1 \cdot m_2}{d^2}$. Knowing that the…
Newton's Law of Universal Gravitation states that the force of attraction between two bodies is given by $F = G \frac{m_1 \cdot m_2}{d^2}$.
Knowing that the gravitational constant is $G = 6,67 \cdot 10^{-11}$ $N \cdot m^2/kg^2$, the mass of the Earth is $m_1 = 5,97 \cdot 10^{24}$ lb, the mass of the Moon is $m_2 = 7,35 \cdot 10^{22}$ lb and the mean distance between their centers is $d = 3,84 \cdot 10^8$ ft, calculate the force of gravity $F$ in Newtons ($N$). Express the result in scientific notation, rounding to two decimal places.
Word problems with scientific notation
Most real problems are a formula you already know, only with huge or tiny numbers. Follow the same routine every time:
When a problem gives a "per" quantity, such as dollars per person or songs per gigabyte, divide the total by the count. For money, just keep the dollar sign: a city budget of $\$2.4 \times 10^{9}$ shared by $8 \times 10^{5}$ people is $0.3 \times 10^{4} = 3 \times 10^{3}$, that is, $\$3{,}000$ per person.
A human red blood cell has an approximate diameter of $7,5 \cdot 10^{-6}$ feet. If in a laboratory experiment we managed to align $4 \cdot 10^6$ red blood cells one…
A human red blood cell has an approximate diameter of $7,5 \cdot 10^{-6}$ feet. If in a laboratory experiment we managed to align $4 \cdot 10^6$ red blood cells one after another, what length in feet would the line reach? Express the result in scientific notation and in standard decimal format.
The mean distance from the Earth to the Sun is about $1,5 \cdot 10^8$ miles and the speed of light in a vacuum is $3 \cdot 10^5$ miles/s. Using the formula for uniform…
The mean distance from the Earth to the Sun is about $1,5 \cdot 10^8$ miles and the speed of light in a vacuum is $3 \cdot 10^5$ miles/s. Using the formula for uniform rectilinear motion ($t = \frac{d}{v}$), how many seconds does it take for sunlight to reach the Earth? Express the result in scientific notation and then convert it to minutes.
The Gross Domestic Product (GDP) of a European country amounts to $\$1,2 \cdot 10^{12}$. If the total population of the country is $4 \cdot 10^7…
The Gross Domestic Product (GDP) of a European country amounts to $\$1,2 \cdot 10^{12}$. If the total population of the country is $4 \cdot 10^7$ inhabitants, what is the GDP per capita (dollars per inhabitant)? Express the result in scientific notation and in standard dollars.
Equations and unit chains
Scientific notation works inside equations too. Use the same inverse operations you use with any linear equation: subtract, then divide.
Many problems also chain several unit conversions. Each conversion factor is itself a number you can write in scientific notation, so multiply them one after another.
Set up and solve the following linear equation in which the coefficients are expressed in scientific notation. Solve for the unknown $x$ and express its value in…
Set up and solve the following linear equation in which the coefficients are expressed in scientific notation. Solve for the unknown $x$ and express its value in scientific notation:
$(2,5 \cdot 10^4) \cdot x + 3 \cdot 10^5 = 1,8 \cdot 10^6$
A glass contains exactly $18$ grams of pure water ($H_2O$). In chemistry, it is known that $18$ grams are equivalent to $1$ mol of water and that $1$ mol of any…
A glass contains exactly $18$ grams of pure water ($H_2O$). In chemistry, it is known that $18$ grams are equivalent to $1$ mol of water and that $1$ mol of any substance contains Avogadro's Number ($6,022 \cdot 10^{23}$) of molecules. From this data, calculate the mass in kilograms of a single water molecule. Express the final result in scientific notation.
A research center needs to transfer a massive backup of $4,5$ Petabytes (PB) to a server in another city. The dedicated fiber optic connection allows data to be…
A research center needs to transfer a massive backup of $4,5$ Petabytes (PB) to a server in another city. The dedicated fiber optic connection allows data to be transferred at a constant speed of $3 \cdot 10^8$ bytes per second. Knowing that $1$ PB is equivalent to $10^{15}$ bytes, calculate how many full days (and fraction of a day if necessary) it will take to finish the transfer. Show the intermediate calculations in scientific notation.
Back to the start: sunlight takes about $5 \times 10^{2}$ seconds, or roughly $8$ minutes, to cross the $9.3 \times 10^{7}$ miles to Earth. Dividing the coefficients and subtracting the exponents did the work, with no counting of zeros.