Question

An element with mass 630 grams decays by 18.8% per minute. How much of the element is remaining after 7 minutes, to the nearest 10th of a gram? round

Answer 1

Use A = A0(1 − r)^t with r = 0.188, t = 7:

A = 630*(0.812)^7 ≈ 630*(0.2327513479) ≈ 146.6333492 g.

Rounded to the nearest tenth: 146.6 g.