Two people A and B started running from the same point on a circular-track of length 400 m in opposite directions with initial speeds of 10 m/s and 40 m/s, respectively. Whenever they meet, A's speed doubles and 3's speed halves. After what time from the start will they meet for the third time?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 26 sec.
First Meeting: Relative speed = 10 + 40 = 50 m/s
Time to first meet = 400/50 = 8 sec
A's new speed = 10 × 2 = 20 m/s and B's new speed = 40 × 2 = 20 m/s
Second Meeting: Relative speed = 20 + 20 = 40 m/s
Time for the second meeting = 400/40 = 10 sec
Total time until the second meeting = 8 + 10 = 18 sec
A's new speed = 20 × 2 = 40 m/s and B's new speed = 20 × 2 = 10 m/s
Third Meeting: Relative speed = 40 + 10 = 50 m/s
Time for the third meeting = 400/50 = 8 sec
Total time until the third meeting = 18 + 8 = 26 sec