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Three bells ring simultaneously at 11 a.m. They ring at regular intervals of 20 min., 30 min., 40 min. respectively. The time when all the three bells ring together next is

Three bells ring simultaneously at 11 a.m. They ring at regular intervals of 20 min., 30 min., 40 min. respectively. The time when all the three bells ring together next is Correct Answer 1 p.m.

Given

Three bells ring simultaneously at 11 a.m. They ring at regular intervals of 20 min., 30 min., 40 min. respectively.

Calculation

In such case take Lcm of the given time

20 = 22 × 5

30 = 2 × 3 × 5

40 = 23 × 5

Lcm of 20, 30 and 40 = 120 

120 min = 2 hours

Three bells will ring together 

⇒ 11 a.m. + 2 hours = 1 p.m.

 

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