In a 400-metre race, A runs at a speed of 16 m/sec. If A gives B a start of 15 metres and still beats him by 10 sec, then what is the speed of B?

11 m/sec

Distance = speed × time

Distance runs by A in 400 m race = 400m

Speed = 16m/sec

Time = \(\frac{Distance }{Speed}\)

= \(\frac{400 }{16}\) = 25sec

As , A beats B by 15 m . So distance runs by B = 385 m

And also A beats B by 10 sec . So time taken by B to runs 385m is 35sec .

So , Speed of B = \(\frac{385 }{35}\) = 11 sec