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?

Answer 1

Rate, $r=18.8\%$

Time, $t=7$

Initial mass, $i=630$

To calculate the remaining element, we apply the formula, $i(1-{r\over100})^t=630(1-0.188)^7=630\times 0.2328=146.6$

Therefore, the remaining element after 7 minutes is 146.6 grams (to the nearest 10th of a gram).