Question

Bryant just drank a cup of coffee to help him stay awake. The coffee had 52 milligrams of caffeine in it. If his body processes 20% of the caffeine every hour, how much will be left in 9 hours?

Answer 1

Let c be caffeine, h be hours, mg milligrams:

c= 52 mg
1h =.2 (52)= 10.4

x/9h=10.4/1h

x= 93.6 mg

93.6- 52= 41.6 mg of caffeine will be left behind.