Aptitude - Problems on H.C.F and L.C.M - Discussion

Can anyone answer for Secotad question?

Very good explanation @Sravanreddy.

Thanks, all of you solvers. It's really useful.

Can anyone explain for Awanish's answer because time starts after 0? Also, I have another sum. A train travels 10days daily. B train travels 10days daily but opposite to A. If a man in A starts 11 am and reaches other station after 10days how many B trains he had passed if starting the train of A = starting time of B ie. , 11 am, thanks.

I hope 16 is not correct, as the question is simply saying how many time the bells will toll together in 30 mins.

We got that they will toll together in every 2 mins so 0-2, 2-4, 4-6, 6-8, 8-10, 10-12, 12-14, 14-16, 16-18, 18-20, 20-22, 22-24, 24-26, 26-28, 28-30.

So seems the answer is 15, if wrong please rectify me.

Can anyone please help me out getting the answer of the below question.

The bells commence tolling together & they toll after 0.25, 0.1 & 0.125 seconds. After what interval will they again toll together?

Friends, Let bells ring together once in 120 seconds.
Let's say they all ring for the first time at 1st sec and they ring altogether once again after 120 sec, say 121st sec.

Therefore they ring at.

1st sec, 121st sec, 241st sec, and this series forms an ap with.

A = 1, d = 120.

Therefore.
Number of terms before 1800 =1 6 (should be) as per answer given.

But the number of terms comes as 15 and the bells ring together at 1801st sec for the 16th time.

Why use 120 seconds? What does it represent?

@Anare: it represents that after every 120sec bells toll together.

As per my calculation, the correct answer is 15.