Activity (Process)

Procedure for Finding Percent Decrease

When a quantity falls from an original value to a smaller new value, the percent decrease expresses the size of that decline relative to the original value. The calculation follows two steps:

  1. Find the amount of decrease by subtracting the new amount from the original amount:

original amountnew amount=decrease\text{original amount} - \text{new amount} = \text{decrease}

  1. Determine what percent the decrease is of the original amount by translating the question "The decrease is what percent of the original amount?" into an equation and solving it. Let pp represent the unknown percent. The equation takes the form:

decrease=p×original amount\text{decrease} = p \times \text{original amount}

Divide both sides by the original amount to isolate pp, then convert the resulting decimal to percent form.

This procedure mirrors the one for percent increase, with one key difference: the subtraction in Step 1 reverses the order — the original amount comes first — so that the result is a positive number representing how much the quantity dropped. As with percent increase, the comparison is always made against the original amount.

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Updated 2026-04-21

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