An element with mass 310 grams decays by 5.7% per minute. How much of the element is remaining after 9 minutes, to the nearest 10th of a gram?

Answer 1

If the 310 mass decays at 5.7% every minute, that means that you are left with 94.3% of the mass after every minute.

So, at the end of the first minute, you will have .943 x 310 = 292.33 g

At the end of the second minute, you will have .943 x 292.33 = .943 x (.943 x 310) = 275.67

At the end of the third minute, you will have .943 x 275.67 = .943 x .943 x (.943 x 310) = 259.95 g

Now you can see the trend, at the end of n minutes, there is (.943)ⁿ x 310 grams

So, after 9 minutes, the amount of material remaining is (.943)⁹ x 310 = 182.8 grams