Three bodies D, E and F start moving around a circular track of length 240m from the same point simultaneously in the same direction at speeds of 6 m/s, 10 m/s and 18 m/s respectively. When will they meet for the first time after they started moving?  Pick one
A) 120 seconds
B) 60 seconds
C) 30 seconds
D) 20 seconds
E) 50 seconds
If they all meet after T seconds, it means they covered the distances 6T, 10T, and 18T respectively.   Since they all arrive to the same spot, it means that the differences taken pairwise between the distances must be positive integer multiples of the length of the track, which is 240m. So, 4T, 8T, and 12T must all be multiples of 240. 4T multiple of 240 means T multiple of 60. The smallest T with this property is 60 and is on the list of answers.   Answer 60 seconds.
<result>B</result>
Three bodies D, E and F start moving around a circular track of length 240m from the same point simultaneously in the same direction at speeds of 6 m/s, 10 m/s and 18 m/s respectively. When will they meet for the first time after they started moving?