Question

If the speeds of Saurav and Sachin were 8 km/hr & 5 km/hr respectively. Then after what time will the two meet for the first time at the starting point if they start simultaneously? The length of the circular track is 500 m.

• A. 60 min
• B. 1800 seconds
• C. 1 hour
• D. 45 min

Answer 1

Answer: (B)

1800 seconds

Let us first calculate the time Saurav and Sachin take to make one full circle

Time taken by Saurav = $\frac{500}{(8\times \frac{5}{18})}$ = 225 s

Time taken by Sachin = $\frac{500}{(5\times \frac{5}{18})}$ = 360 s

Hence, after every 225 s Saurav would be at the starting point and after every 360 s 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 LCM of $225$ and $360=1800$ s.

Thus after every half an hour they would meet at the starting point.From the solution you could realize that it is immaterial whether they move in the same direction or in the opposite direction.