M and N walk along a circular track. They start at 5:00 a.m. from the same point in the opposite directions. M and N walk at a speed of 5 rounds per hour and 2 rounds per hour, respectively. How many times will they cross each other before 6.30 a.m. on the same day?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 10.
From 5:00 a.m. to 6:30 a.m., the total walking time = 6 : 30 - 5 : 00 = 1.5 hours
M walks at 5 rounds/hr
N walks at 2 rounds/hr
They walk in opposite directions so,
Relative speed = 5 + 2 = 7 rounds/hr
So,
Distance = Speed × Time
⇒ 7 × 1.5 = 10.5 rounds
M and N cross each other once for every round of relative distance covered.
Therefore,
Number of crossings = 10