Time taken by each of them to complete one round =
Circumference of the circle
speed
Time taken for Ram to cover one round =
2π×100
15×5/18
=48π Time taken for Rahim to cover one round =
2π×20
5×5/18
=28.8π Time taken by Ram and Rahim meet each other for the first time =LCM of 48π and 28.8π=144π ∴ Number of rounds made by Ram before he meets Rahim for the first time =