UPSC CDS Math Speed, Time and Distance Questions

Speed of the thief=8×

5

18

=

20

9

m/s
Speed of the policeman=10×

5

8

=

25

9

m/s
Suppose the policeman catches thethief after t seconds.
Distance covered by the policeman in t seconds = 100 m + Distance covered by the thief in t seconds
∴

25

9

t=100+

20

9

t
⇒

5

9

t=100
⇒t=

100×9

5

=180seconds
Therefore, the distance run by thethief before the policeman overtakes him=

20

9

×180=400m