P can complete a round of circular track in 1 minute and 30 seconds while Q can complete a round in 45 seconds. If they start moving from the same point and move in opposite directions, then they meet after _____ seconds.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 30.
Time taken by P to complete 1 round = 1 minute 30 seconds = 90 seconds
Time taken by Q to complete 1 round = 45 seconds
They move in opposite directions from the same point.
Let the length of the circular track = L units
P's speed = L / 90
Q's speed = L / 45
Relative speed = (L/90) + (L/45) = (1 + 2) × L / 90 = 3L/90 = L/30
Time = Distance / Relative Speed
They meet when they cover 1 full round together, i.e., distance = L
Time = L / (L/30) = 30 seconds