Percent

Sommaire

In short: Percent is a rate per 100, so 35 percent means 35 out of every 100 and can be written as 35%, the fraction 35/100 or the decimal 0.35.

6th GradeRatios and Percents6.RP.A.3c

What is Percent?

The word percent comes from “per hundred”. It lets you compare amounts of very different sizes on one common scale, as when a quiz score and a battery level are both shown out of 100.

Precisely, $p\%$ means $\frac{p}{100}$. To find $p\%$ of a quantity $W$, compute $\frac{p}{100} \cdot W$. If a part $P$ is taken from a whole $W$, its percent is $\frac{P}{W} \times 100$.

How to spot it

A story shows the % sign or phrases like “out of every 100”.
You must find a part of a quantity, such as 15% of a $60 price.
A problem gives a part and a rate per 100 and asks for the whole amount.
A grid of 100 squares is partly shaded and you must say how much is covered.

The method

Turn the rate into a fraction over 100 or a decimal: $35\% = \frac{35}{100} = 0.35$.
To find a part, multiply the whole by that fraction or decimal.
To find the whole, divide the known part by the decimal form of the percent.
To go from a part and a whole to the rate, divide part by whole and multiply by 100.

Thirty-five of the hundred squares are shaded, which is 35 percent.

Percent: solved example

Problem

A soccer club in Portland has 80 players, and 45% of them play defense. How many play defense?

Solution

Write the rate as a decimal: $45\% = 0.45$.

Multiply by the whole: $0.45 \times 80 = 36$. The club has 36 defenders.

Try it

Question 1

A survey reaches 18 people out of 24 who prefer pizza. What percent is that?

Show the answer

$\frac{18}{24} = 0.75$, and $0.75 \times 100 = 75$, so the answer is 75%.

Question 2

A phone is charged to 27 minutes of talk time, which is 30% of its full life. How many minutes is the full life?

Show the answer

$27 \div 0.30 = 90$, so the full life is 90 minutes.

Percent vs. Ratio

This one always compares a part to 100, so its second number never changes. A general ratio can use any second number, like 7 to 12. Converting a ratio means finding the equivalent ratio with 100 as the second term.

Ratio

Keep going

Lessons

Percent as a Rate per 100

Worksheets and quizzes

Related words

Whole dictionary: A–Z · 6th Grade · Ratios and Percents

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