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 previous one.How long does she take to run 3 laps?

Answer 1

182 seconds

Explanation:

Given:

Time taken for first lap is 50 seconds and each subsequent lap takes 20% longer than previous

Solution:

Time taken for first lap = 50 sec

For second lap

Each subsequent lap takes 20% longer than previous

Previous lap time = 50 sec

second lap = 50 + 20% of 50

second lap
`=50+((20)/(100)* 50)`

second lap
`= 50 + 10`

second lap
`= 60\ sec`

For third lap

Each subsequent lap takes 20% longer than previous

Previous lap time = 60 sec

Third lap = 60 + 20% of 60

`Third\ lap = 60 + ((20)/(100)* 60)`

`Third\ lap = 60+2* 6`

`Third\ lap = 60+12`

`Third\ lap = 72\ sec`

Time taken for 3 laps is equal to sum of all three laps time.

`Tiem\ taken\ for\ 3\ lap = 50+60+72`

`Tiem\ taken\ for\ 3\ lap = 182\ sec`

Therefore, it takes 182 seconds (3 min, 2 seconds) to run three laps