Two boys start jogging together on a circular track. If they respectively take 30 minutes and 20 minutes to complete one round, when will they meet ?
A
after 50 minutes
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B
after 60 minutes
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C
after 40 minutes
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D
after 90 minutes
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Solution
The correct option is B after 60 minutes Prime Factorisation of 30 = 2 x 3 x 5
Prime Factorisation of 20 = 2 x 2 x 5
Least common multiple of 20 & 30 is 2 x 2 x 3 x 5 = 60 minutes ∴ Both boys will meet after 60 minutes.