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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?

A 182 seconds
Explaination

If the first lap takes 50 seconds, the second one takes 20% more, or $3461_w242_h14.png$ seconds, where T1 and T2 are the times required for the first and second laps, respectively. Similarly, $9611_w242_h14.png$ seconds, the time required for the third lap. Add the times for the three laps: 50 + 60 + 72 = 182.