Six bells start ringing together and ring at intervals of 4, 8, 10, 12, 15 and 20 seconds respectively. how many times will they ring together in 60 minutes ?

A) 31 B) 15 C) 16 D) 30

Answer & Solution

Correct Answer: Option A

LCM of 4, 8, 10, 12, 15 and 20 = 120
120 seconds = 2 minutes
Hence, all the six bells will ring together in every 2 minutes
Hence, number of times they will ring together in 60 minutes
= $$1 + \frac{{60}}{2}$$
= 31

Question posted by Examveda

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4 Comments

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Sathi Tmp 7 years ago

Could you please explain why 1 is being added .

Kumar Chandan 11 years ago

When they start ringing, it was zero minutes. Say if they start 1 PM, then they rings at 1PM then 1:02 and so on. Understand @Palak?

Palak Grover 11 years ago

if 2 minutes they ring together then in 60 min 60/2 but why 1 is being added?

Palak Grover 11 years ago

if 2 minutes they ring together then in 60 min 60/2 but why 1 is being added?

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Six bells start ringing together and ring at intervals of 4...

Six bells start ringing together and ring at intervals of 4, 8, 10, 12, 15 and 20 seconds respectively. how many times will they ring together in 60 minutes ?

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