Question

A medicine is decaying at a rate of 5% per hour. If there were initially 1000mg of the medicine, how much is left after 4 hours? Round to the nearest tenth

(one decimal place)
Write an equation first, then plug in the value 4 for X

Answer 1

814.5 mg remain after 4 hours

Explanation:

The multiplier of the original quantity is 1 -5% = 0.95 for each passing hour. The amount remaining after x hours is ...

y = 1000·0.95^x

For x=4, the amount remaining is ...

y = 1000·0.95^4 = 1000·0.81450625

y ≈ 814.5 . . . mg remain after 4 hours