Question

On Monday, the pollen count was 320 grains per cubic meter. On Tuesday, the pollen count was 15% less. What was the pollen count on Tuesday?

Answer 1

The pollen count on Tuesday was 272 grains per cubic meter.

Explanation:

The formula for calculating the percent change is `p = (N - O)/O * 100` where `p` is the percent change, `N` is the new value and `O` is the old value. Substituting what we know gives:

`-15 = (N - 320)/320 * 100`

Solving for `N` gives:

`-15/100 = (N - 320)/320`

`(-15 * 320) / 100 = N - 320`

`-4800 / 100 = N - 320`

`-48 = N - 320`

`320 - 48 = N`

`N = 272`