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

Answer:

182 seconds

Step-by-step 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 $=50+(\frac{20}{100}\times 50)$

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

$Third\ lap = 60 + (\frac{20}{100}\times 60)$

$Third\ lap = 60+2\times 6$

$Third\ lap = 60+12$

$Third\ lap = 72\ sec$

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