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Chapter 9 · Questions · page 50 of 68

How do you calculate percent increase or decrease?

Short answerFind the change, divide it by the original number, and multiply by 100. From 48 to 60 is a change of 12, and 12 ÷ 48 is 25%.

levelPre-algebra
standard7.RP.A.3
practiceDecimals and percents

Percent change compares the change to where you started, so the original number always goes on the bottom. The same formula works for decreases. The change is just in the other direction.

How to use it

  1. Subtract to find the change.
  2. Divide the change by the original number, the one you started with.
  3. Multiply by 100 and say whether it went up or down.

Example

60−48=1260 - 48 = 12
1248=0.25\frac{12}{48} = 0.25
0.25×100=250.25 \times 100 = 25

Where it goes wrong

  • Dividing by the new number instead of the original.
  • Reporting the change itself, 12, as the percent.

Related

Percent change and discountsPercent of a number
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