Question

Two toy trains start at the same time. The first one stops after every 5 seconds and the second one stops after every 4 seconds. How many times do they stop together in 1 minute ? (A) 4 (B) 2. (C) 3 (D) 5​

Answer 1

Answer:

Given the first train completes one round of a circular track in 120 seconds and the second train does so in 180 seconds.

Now both trains move in the opposite direction in order to find time after which they will meet for the first time we need to take LCM(120,180)

120=2

3

×3×5

180=2

2

×3

2

×5

∴LCM(120,180)=360seconds=

60

360

=6min

∴ the two trains meet for the first time after 6 mins from where they started.