SOLUTION: An element with mass 970 grams decays by 27.7% per minute. How much of the element is remaining after 13 minutes, to the nearest 10th of a gram?

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Question 1179624: An element with mass 970 grams decays by 27.7% per minute. How much of the element is remaining after 13 minutes, to the nearest 10th of a gram?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39623) About Me  (Show Source):
You can put this solution on YOUR website!
In what way do you need to solve this? 
TIME       AMOUNT PRESENT
  0              970
  1              706.2
  2              514.1
  3              374.3
  4              272.5
  5              198.3
  6              144.4
  7              105.1
  8               76.5
  9               55.7
  10              40.6
  11              29.5
 12               21.5
 13               15.6

Answer by ikleyn(52835) About Me  (Show Source):
You can put this solution on YOUR website!
.

The formula for the mass M(n) remaining after n years is


    M(n) = 970%2A%281-0.277%29%5En = 970%2A0.723%5En.


After 13 years


    M(13) = 970%2A0.723%5E13 = 14.31 = 14.3  grams  (rounded).     ANSWER

Solved.