You run 100 meters in 15 seconds, 400 meters in 1 minute, and 800 meters in 2 minutes. How long will it take you to run 1 kilometer if you continue...

The time taken to run 100 m is 15 seconds. To run 400 m the person needs 1 minute which is 4*15 = 60 s. To run 800 m, 1*2 = 2 minutes is required.

In all the three cases the speed of the person does not change; it is constant at 400/60 = 20/3 m/s.

The time required to run 1 km is `1000/(20/3)` = 150 seconds.