Question

A long distance runner does a first lap around a track in exactly 50 seconds. As she tires, each subsequent lap takes 20% longer than the previous one. How long does she take to run 3 laps?

Answer 1

Since only a few laps are involved, you can simply add up the times.
The second lap will take 50*1.2 = 60 seconds.
The third lap will take 60*1.2 = 72 seconds.

The total time for 3 laps will be (50 +60 +72) seconds = 182 seconds.