A and B take part in a 100 metres race. A runs at 5 km an hour. A gives B a start of 8 metres and still beats him by 8 seconds. The speed of B is ?

Answer: Option B

A's speed = 5 km/hr
= $$\left(5\times \frac{5}{18}\right)$$  m/sec
= $$\frac{25}{18}$$ m/sec
Time taken by A to cover 100 metres
= $$\left(100\times \frac{18}{25}\right)$$
= 72 sec
Time taken by B to cover 92 metres
= (72 + 8) sec
= 80 sec
B's speed
$$\frac{92}{80}$$ m/sec
= $$\left(\frac{92}{80}\times \frac{18}{5}\right)$$  km/hr
= $$\frac{414}{100}$$ km/hr
= 4.14 km/hr