Question

A cup of coffee contains 130 mg of caffeine. If caffeine is eliminated from the body at a rate of 11% per hour, how much caffeine will remain in the body after 3 hours?

Answer 1

91.646 mg ( approx ) of coffee will remain.

Explanation:

Given,

Initial quantity of coffee in the body, a = 130 mg,

Rate of decreasing per hour, r = 11 %,

Thus, the remained quantity of coffee after 3 hours,

`A=a(1-(r)/(100))^3`

`=130(1-(11)/(100))^3`

`=130((89)/(100))^3`

`=130(0.89)^3`

`=91.64597\approx 91.646\text{ mg}`

Answer 2

A=p (1-r)^t
A=130×(1−0.11)^(3)
A=91.65