Question

four Bells toll at intervals of intervals of 8 9 12 and 15 minutes respectively if they toll together next

Answer 1

The answer is 6 hours

Answer 2

Given that, four bells toll after an interval of 8,9,12,15 minutes ,respectively. These bells begin to toll together at 3.p.m. We have to find the time at which they toll again.
For this, first we have to calculate the L.C.M of given numbers.
Factors of  8 are 2 x 2 x 2
Factors of  9  are 3 x 3
Factors of 12 are 2 x 2 x 3
Factors of 15 are 3 x 5
Common factors are 2 x 2 x 3 x 2 x 3 x 5
Hence, L.C.M = 360
Which shows that the four balls toll together after 360 minutes.
Now we convert these minutes into hours.
We know that,
60 minutes = 1 hour
360 minutes = (1 / 60 ) . 360
                     = 6 hours
As it is given that the bells begin to toll together at 3 p.m
So next toll will be after 6 hours.
Thus 3 p.m + 6 hours
which clearly shows that the bells toll together again at 9 p.m