At a call center, Bob makes a call every 12minutes, Bill makes a call every 18minutes, and Brad makes a call every 30minutes. If they all simultaneously make a call at 3:00 PM, how many hours later will they all simultaneously make a call for the third time . Could someone explain the solution for this

Hint: LCM

After solving I got Lcm as 180 and converting that to hours it is 3 , but the solution given is 6 . Also is there a way to find from the question when to use Lcm and hcf

You made a trivial mistake in that case. Read the question carefully.

Unable to figure out the mistake. Please explain where did I go wrong

What happens 3 hours later?

All 3 will make a call simultaneously?

Correct. Now what is the question asking?

How many hours later they all make a call for third time?

Yes. They make the first call at 3 pm. When do they make the call for the second time? How about the third time?

Second time - 6pm , Third time - 9pm ?

Correct. Do you now know what the answer to the question is?

Yeah got it they are asking the difference of hours between 9pm & 3pm so it is 6?

Indeed.

Thank you!!