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Six bells start ringing simultaneously and they ring at intervals of 4, 8, 10, 12, 18 and 20 seconds respectively. Once the ringing starts, how many times will the bells ring together in next 30 minutes?

Six bells start ringing simultaneously and they ring at intervals of 4, 8, 10, 12, 18 and 20 seconds respectively. Once the ringing starts, how many times will the bells ring together in next 30 minutes? Correct Answer 5 times

Given:

Bells are ringing at a interval of 4, 8, 10, 12, 18 and 20 seconds

Concept Used:

All bells ring simultaneously after the LCM of all single ring

Calculation:

LCM of (4, 8, 10, 12, 18 and 20) = 360 sec

We know that,

60 second = 1 minutes

Six bells for first time ringing simultaneously in 6 minutes

∴ In 30 minutes they ringing simultaneous = 30/6  = 5 times

Mistake Points 

Here we were asked to count the number of times bells rang after the ringing starts. So, we will not add 1 here.

If the question is stated like this ---> Six bells start ringing simultaneously and they ring at intervals of 4, 8, 10, 12, 18, and 20 seconds respectively. How many times will the bells ring together in 30 minutes?

Then our answer will be 6.

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