Question

An element with mass 130 grams decays by 22% per minute. How much of the the element is remaining after 7 minutes, to the nearest 10th of a gram?

Answer 1

`22.8 color(white)(l) "g"`

Explanation:

The sample decays by `22%` each minute, indicating that the mass at the beginning of the next minute would be `1-22%=78%` the mass at the beginning of this minute.

This process repeats for seven times in the `7 color(white)(l) "minutes"`. That is

`130 color(white)(l) "g" xx (1-22%)^7=22.8 color(white)(l) "g"`