Question

Three students start jogging together on a circular track if they respectively take 6minutes 8minutes,12minutes to complete one round, when they meet again

Answer 1

I guess the answers is 18 minutes

Answer 2

As given they start jogging together and take 6 minutes, 8 minutes and 12 minutes to complete one round respectively.
the first time when they would meet after they had started, will be the LCM of the given time taken by them to complete one round.
L.C.M of 6, 8 and 12.
6 = 2*3
8 = 2*2*2
12 = 2*3*2
L.C.M = the  distinct factors with the highest powers.
Thus, L.C.M = 2*2*2*3 = 24
Thus they meet after 12 minutes after starting.
Hope this helps.