Question

An element with mass 780 grams decays by 17.1% per minute. How much of the element is remaining after 19 minutes, to the nearest 10th of a gram?

Answer 1

22.1 grams

Explanation:

At the end of each minute, (1 -17.1%) = 82.9% of the element remains. At the end of 19 minutes, the quantity has been multiplied by that value 19 times, so the remaining amount is ...

(780 g)(0.829^19) ≈ 22.1 g

After 19 minutes 22.1 grams remain.