Question

13. Four bells toll at intervals of 4,7,12 and 84 seconds. The bell toll together at 5
o'clock. When will they again toll together?​

Answer 1

They will toll together for a 'common multiple' of (4,7,12,84), which is the l.c.m of these numbers.

4== 2^2

7 == 7

12 = 2^2 * 3

84 = 12 * 7 = 2^2 * 3 * 7

l.c.m(4,7,12,84) = 2^2 * 3 * 7 = 84 s

84 s = 1 min 24 sec

Hence they will toll together 84 seconds after 5 o'clock or 5:01:24 hrs ( 1 min 24 sec past 5 o'clock)

28 mins = 28*60 = 1680 sec

84 sec== toll 1 time

1680 sec== X times

X = 20 times

Hence,

They toll together at 5:01:24 hrs

In 28 mins they toll (together) 20 times.

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Answer 2

Answer:

Step-by-step explanation.