Question

Four bells toll at intervals of 4.,7.,12 and 84 seconds. The bells toll together at 5 oclock. When will they again
togethet? How many times will they do in 28 minutes?
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Answer 1

Answer:

How many times 'll they do it in 28 mins. Find LCM 4, 7, 12 and 84. LCM - 84. so the bells will toll again together at 5:1:24 am/pm.

Step-by-step explanation:

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.

Hope it helps.

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