Curt just drank a cup of coffee to help him stay awake. The coffee had 130 milligrams of caffeine in it. If his body processes 7% of the caffeine every hour, how much will be left in 4 hours?
After 4 hours, his body will have processed 28% because 74 = 28. But, you're trying to find what's left (so, subtract that % from 100)
100%-28% = 72%
Then multiply the percent left by the total number of milligrams of caffeine
130.72 = 93.6 mg
Answer: 97.25 milligrams
Step-by-step explanation:
Given: Curt just drank a cup of coffee to help him stay awake.
The initial amour of caffeine in coffee= 130 milligrams
The rate of decay of caffeine in body = 7%= 0.07
We know that the exponential decay equation with rate r and and time t is given by :-
\(f(x)=A(1-r)^t\), where A is the initial value.
Now, the amount of caffeine left in body after 4 hours is given by :-
\(f(4)=130(1-0.07)^4\\\\\Rightarrow\ f(4)=97.2467613\approx97.25\text{ milligrams}\)
Hence, after 4 hours 97.25 milligrams will be left.