A ship travelling towards a cliff receives the echo of its whistle after 3.5 seconds. A short while later, it receives the echo after 2.5 seconds. If the speed of sound in air under the prevalling condition is 250ms -1, how much closer is the ship to the cliff?

A. 10m
B. 350m
C. 175m
D. 125m

Correct Answer:

Option D = 175m

Explanation

Difference in time = 1 sec

echo time = 1 ÷ 2 = 0.5 sec

Difference of cliff from ship = 0.5 x 250

= 125m