Question

Chris drank a cup of coffee with 150 milligrams of caffeine. Each hour the caffeine in Chris' body diminishes by about 9%. How long after the coffee is consumed will it take for the caffeine in Chris' system to drop below 25 mg? Round your answer to the nearest hour.

Answer 1

So for this problem, we can simply subtract 9% of the caffeine left in Chris' body repeatedly until we get below 25 and count up how many times we had to subtract.