Scientific Notation
The mass of the Earth is $5{,}970{,}000{,}000{,}000{,}000{,}000{,}000{,}000$ kg. The mass of an electron is $0.00000000000000000000000000000091$ kg. Nobody wants to count all those zeros by hand, and one missing zero makes your answer wrong by a factor of 10. Scientists, engineers, and data analysts write these numbers with powers of $10$. Can you write both masses with just a few digits each? By the end of this page you will.
What Is Scientific Notation?
Why $1 \le a < 10$? It makes the notation unique. There is only one way to write each number, so numbers are easy to compare. The exponent $n$ tells you the size of the number, and the coefficient gives its digits.
Scroll through the scales of the universe, from atoms to galaxies, all on one logarithmic line:
Indicate which of the following numbers are not correctly written in standard form 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 standard form 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 Notation and Decimals
The exponent counts how many places the decimal point moves.
Write the following decimal numbers in standard form: a) $450 000 000$ b) $0,000000032$ c) $12 500$ d) $0,000105$
Write the following decimal numbers in standard form:
- a) $450 000 000$
- b) $0,000000032$
- c) $12 500$
- d) $0,000105$
Express the following numbers given in standard form as ordinary decimal numbers: 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 standard form as ordinary decimal numbers:
- 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 Numbers
The exponent decides first. Only when the exponents are equal do you compare the coefficients.
Order of magnitude
The order of magnitude of a number is the power of $10$ closest to it. Between $10^{n}$ and $10^{n+1}$, the halfway point on the number line is $5.5 \times 10^{n}$. So for a number $a \times 10^{n}$:
-
if $a < 5.5$, the order of magnitude is $10^{n}$;
-
if $a > 5.5$, the order of magnitude is $10^{n+1}$.
Many classes simply say "round up when $a \ge 5$." The two rules agree except for coefficients between $5$ and $5.5$, so it is fine to use that shortcut. On this page we use the nearest power of $10$ on the number line.
Order the following numbers written in standard form from smallest to largest: $A = 3,2 \cdot 10^4$ $B = 4,1 \cdot 10^{-3}$ $C = 1,5 \cdot 10^4$ $D = 8,9 \cdot 10^{-4}$…
Order the following numbers written in standard form from smallest to largest:
$A = 3,2 \cdot 10^4$
$B = 4,1 \cdot 10^{-3}$
$C = 1,5 \cdot 10^4$
$D = 8,9 \cdot 10^{-4}$
$E = 2 \cdot 10^5$
Determine the order of magnitude (the nearest power of $10$) of the following quantities expressed in standard form: 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 standard form:
- 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
Handle the coefficients and the powers of $10$ separately. Use the product and quotient rules for powers: $10^m \cdot 10^n = 10^{m+n}$ and $10^m \div 10^n = 10^{m-n}$. At the end, adjust the coefficient if it falls outside $[1, 10)$.
Why does adjusting work? $24 \times 10^5 = 2.4 \times 10 \times 10^5 = 2.4 \times 10^6$. Each time the coefficient gets $10$ times smaller, the exponent goes up by $1$, and the value stays the same.
Perform the following multiplications by grouping the numbers and the powers of base $10$. Express the final result in standard form: a)…
Perform the following multiplications by grouping the numbers and the powers of base $10$. Express the final result in standard form:
- 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 standard form: 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 standard form:
- 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 standard form:…
Solve the following combined operation respecting the order of operations and give the final result adjusted in standard form:
$\frac{(4,2 \cdot 10^5) \cdot (2 \cdot 10^{-3})}{3 \cdot 10^4}$
Adding and Subtracting
Adding and subtracting works like combining like terms: you can only combine numbers that have the same power of $10$. If the exponents are equal, add or subtract the coefficients and keep the power of $10$. If they differ, rewrite one number first.
When the expression is a fraction with sums on top or bottom, simplify the top and the bottom separately, then divide.
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 standard form:…
Calculate the following additions and subtractions with different exponents, first adjusting the powers of $10$ so that they match. Express the result in standard form:
- 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 standard form:…
Carry out the following combined operation with additions and subtractions in the numerator and denominator. Express the final result strictly in standard form:
$\frac{3,6 \cdot 10^{12} + 4,1 \cdot 10^{11}}{2 \cdot 10^{-3} - 5 \cdot 10^{-4}}$
Solving Equations with Scientific Notation
Solving works exactly as it always does: use inverse operations on both sides. The only new part is that the arithmetic uses the rules above.
Set up and solve the following linear equation in which the coefficients are expressed in standard form. Solve for the unknown $x$ and express its value in standard…
Set up and solve the following linear equation in which the coefficients are expressed in standard form. Solve for the unknown $x$ and express its value in standard form:
$(2,5 \cdot 10^4) \cdot x + 3 \cdot 10^5 = 1,8 \cdot 10^6$
Word Problems: Counts, Rates, and Time
Big-number problems are almost always multiply (how many in total?) or divide (how many fit? how long?). Always write each quantity in scientific notation with its unit, then check that the units cancel to give the unit you want.
A human red blood cell has an approximate diameter of $7,5 \cdot 10^{-6}$ meters. 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 $7,5 \cdot 10^{-6}$ meters. If in a laboratory experiment we managed to align $4 \cdot 10^6$ red blood cells one after another, what length in meters would the line reach? Express the result in standard form and in ordinary 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 standard form and then convert it to minutes.
An external hard drive has a storage capacity of $2$ Terabytes (TB). If a high-resolution photograph takes up an average of $4 \cdot 10^6$ bytes, what is the maximum…
An external hard drive has a storage capacity of $2$ Terabytes (TB). If a high-resolution photograph takes up an average of $4 \cdot 10^6$ bytes, what is the maximum number of photographs that can be stored on this hard drive?
Fact: Consider that $1$ TB is equivalent to $10^{12}$ bytes.
Word Problems: Per-Unit Amounts, Ratios, and Unit Conversion
Dividing one quantity by another gives a per-unit amount (like dollars per person, called per capita). Dividing two quantities of the same kind tells you how many times larger one is than the other.
The Gross Domestic Product (GDP) of a 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 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 standard form and in ordinary dollars.
In particle physics, it is known that the mass of an electron is approximately $9,1 \cdot 10^{-31}$ kg and the mass of a proton is about $1,67 \cdot 10^{-27}$ kg.…
In particle physics, it is known that the mass of an electron is approximately $9,1 \cdot 10^{-31}$ kg and the mass of a proton is about $1,67 \cdot 10^{-27}$ kg. Calculate how many times more massive a proton is than an electron. Express the solution in standard form to two decimal places.
A water reservoir for human consumption contains $4,5 \cdot 10^3$ cubic hectometers ($hm^3$). Knowing that $1$ $hm^3$ is equivalent to $10^9$ liters, express the total…
A water reservoir for human consumption contains $4,5 \cdot 10^3$ cubic hectometers ($hm^3$). Knowing that $1$ $hm^3$ is equivalent to $10^9$ liters, express the total capacity of the reservoir in liters using standard form. If the city it supplies consumes $5 \cdot 10^7$ liters of water daily, for how many days are there sufficient reserves?
Powers of Numbers in Scientific Notation
Many science formulas square or cube a quantity, such as $v^2$ in kinetic energy, $R^3$ in the volume of a sphere, or $2^t$ in population growth. To raise a number in scientific notation to a power, raise the coefficient to that power and multiply the exponents (the power-of-a-power rule $(10^n)^k = 10^{nk}$).
Changing the units of a length, an area, or a volume
Sometimes the radius is given in one unit but the answer must be in another. For example, a radius in miles and a volume in cubic kilometers. The safest plan is to convert the length first, then use the formula. Use $1\ \text{mi} \approx 1.609\ \text{km}$ (or the factor the problem gives you).
To make astronomical estimates, the Earth can be approximated to 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 to 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 standard form, 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 kg and $v$ is the speed in m/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 kg and $v$ is the speed in m/s. Calculate the kinetic energy of an asteroid of mass $m = 4,5 \cdot 10^{14}$ kg traveling through space at a speed of $v = 2 \cdot 10^4$ m/s. Express the result in Joules (J) using standard form.
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 standard form. (Helpful fact: $2^{10} = 1024$).
Multi-Step Science Problems
Real science problems combine everything: formulas with products and quotients, powers, and unit conversions. Use a plan.
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 $m_1 = 5,97 \cdot 10^{24}$ kg, the mass of the Moon is $m_2 = 7,35 \cdot 10^{22}$ kg and the mean distance between their centers is $d = 3,84 \cdot 10^8$ m, calculate the force of gravity $F$ in Newtons ($N$). Express the result in standard form, rounding to two decimal places.
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 standard form.
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 standard form.
Back to the start: the mass of the Earth is $5.97 \times 10^{24}$ kg, and the mass of an electron is $9.1 \times 10^{-31}$ kg. Two numbers with dozens of zeros each now fit in a few characters, and you can compare them at a glance: the exponents differ by $24 - (-31) = 55$.