A and B take part in a 100 m race. A runs at 5 Km/h. A gives B a start of 8 m and still beat him by 8 sec. Speed of B is :

A's speed = (5 * 5 / 18) m/sec = 25 / 18 m/sec
Time taken by A to cover 100 m = (100 * 18 / 25) sec = 72 seconds.
∴ B covers 92 m in 72 + 8 = 80 seconds.
B's speed = (92 / 80 * 18 / 5) Km/h = 4.14 Km/h.