- A gives B a start of 10 metres in a 100 metre race and still beats him
by 1.25 seconds. How long does B take to complete the 100 metre race if A
runs at the rate of 10 m/sec?
(1) 8 seconds (2) 10 seconds (3) 16.67 seconds (4) 12.5 seconds
Solution:
A gives B a start of 10 metres in a 100 metre race. This means that when A runs
100 metres, B runs only 90 metres.
Despite that start, A beats B by 1.25 seconds.
As A is running at the speed of 10 m/sec, he will take 10 seconds to complete
the 100 metre race. And B takes 10 + 1.25 = 11.25 seconds to cover 90 metres.
Therefore, the speed at which B is running
= 8 m/sec.
Running at 8 m/sec, B will take 100/8= 12.5 seconds to complete the 100 metre race.
Hence the correct answer is (4).
