A thief, seeing a policeman from a distance of 120 metres, starts running at a speed of 7 km/h. The policeman chases immediately with a speed of 8 km/h and the thief is caught. What is the distance run by the thief?

840 m

Distance b/w thief and policeman = 120 m

Relative speed = 8 - 7 = 1 km/h

1 km/h = 1 × \(\frac{5}{18}\) m/sec = \(\frac{5}{18}\) m/sec

Time taken to cover 120 m = \(\frac{120 × 18 }{5}\) = 432 sec

Speed of thief = 7 × \(\frac{5}{18}\)  m/sec = \(\frac{35}{18}\) m/sec

Distance traveled by thief in 432 sec = 432 × \(\frac{35}{18}\)

= 840 m

So , thief covered 840 m before caught by policeman.