Time problems

Question

A, B and C start at the same time in the same direction to run around a circular stadium. A completes a round in 252 seconds, B in 308 seconds and c in 198 seconds, all starting at the same point. After what time will they again at the starting point ?

 

whoever can solve this, would you please explain the steps? like when to take lcm and when to take hcf in such problems? 

Answer 1

I think they are asking when will they all be at the starting point

at the same time again.  If this is the case, you would need the 

least common multiple of: 252, 308, 198

 

This would occur at 2772 seconds