Answer:
3.33hours
Explanation:
you have a total of 60mg, it is asked how much hours it takes to remove half the caffeine which is 30mg
1 hour removes 15%, 15% of 60 is 9g
(15/100×60) = 9
now it removes only 9g in an hour, we have to find out how long (hours) it'll take to remove 30g
30÷9= 3.33 hours