IBPS Clerk Prelims Model Paper 8

Let us first calculate the time Saurav and Sachin take to cover one full circle.
Time taken by Saurav =

500

8× 5 18

=

1800

8

= 225 seconds
Time take by Sachin =

500]

(5× 5 18 )

= 360 seconds
Hence, after every 225 seconds, Saurav would be at the starting point and after every 360 seconds, Sachin would be at the starting point. The time when they will be together again at the starting point simultaneously for the first time would be the smallest multiple of both 225 and 360, which is the LCM of 225 and 360.
Hence, they would both be together at the starting point for the first time after LCM (225, 360) = 1800 seconds = 0.5 hour.
Thus, every half an hour, they would meet at the starting point.