Two buses start from the same spot for the same circular root. One is a BRTS bus returning in 35 minutes. The other is a regular express bus taking 42 minutes to return. After how many minutes will they meet again at the same initial spot?

Given that the BRTS bus returns in 35 minutes and the express bus returns in 42 minutes.

So, we can say that the BRTS returns in the time intervals which are multiples of 35 and the express bus returns in the time intervals which are multiples of 42.

Therefore, both the buses meet at the time interval of l.c.m. of 35 and 42.

35 = 5 × 7

42 = 2 × 3 × 7

l.c.m.(35, 42) = 5 × 2 × 3 × 7 = 210 minutes

So, both the buses will meet after 210 minutes at the initial spot.