In a 100m race A runs at a speed of 9 km/ hr. He gives a start of 10m to B and still defeats him by 10 sec. Find speed of B (in m/sec) .
Answer & explanation
Correct answer: option 4
Total length of race = 100m
Speed of A = 9 km/hr = 9 × \(\frac{5}{18}\) m/sec = \(\frac{5}{2}\) m/sec
Time taken by A to complete the race = \(\frac{100}{\frac{5}{2}}\) = 40 sec
According to question ,
B takes 10sec more to run the whole race
∴ Time taken by B to cover the race = 50 sec
As A gives 10m start to B of 10m
∴ Speed of B = \(\frac{90}{50}\) m/sec = 1.8 m/sec