Three runners on a circular track

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Question from Arul:

Please help me on this question.
A, B and C run around a circular track starting from the same point simultaneously and in the same direction at speeds of 4 kmph, 6 kmph and 8 kmph respectively. If the length of the track is 400 meters, when will A, B and C meet at the starting point for the first time after they started the race?
1 minute
5 minutes
12 minutes
20 minutes
24 minutes

4 In the above question, when will they meet for the first time after they started the race?
1 minute
5 minutes
12 minutes
20 minutes
24 minutes

Thanks
Arul

Hi Arul,

For the first problem the important numbers are the times it takes the runners to circle the track. 400 meters is 0.4 km so the first runner travels 400 metres at 4 km/hr so it takes him

0.4/4 km × hr/km = 0.1 hr.

There are 60 minutes in an hour so 0.1 hr is 6 minutes. Hence the first runner is at the starting point at 6 min, 12 min, 18 min, ...

Find the time it takes each of the other two runners to circle the track.

Penny

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