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Answer:
a) 13%
b) 65.9%
Explanation:
a) You can use n=1 to find the percentage remaining at the end of 1 hour:
P = 100(0.87^1) = 87
This is 13% less than 100%, so the decay rate per hour is 13%.
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b) Fill in n=3 and evaluate the expression.
P = 100(0.87^3) = 65.8503
After 3 hours, about 65.9% of the caffeine remains.