4 Bells toll together at 11:00 A.M. They toll after 7, 8, 10 and 18 se

SOLUTION

There are 4 Bells toll together at 11:00 A.M. They toll after 7, 8, 10 and 18 seconds respectively.

We will first calculate LCM of 7,8,10,18

7 = 1×7

8 = 2×2×2

10 = 2×5

18 = 2×3×3

LCM (7,8,10,18) = 7 × 2 × 2 × 2 × 5 × 3 × 3 = 2520 seconds = 42 mint

So they will toll together after every 42 mint.

Now we are interested in finding that how many times will they toll together again in the next 4 hours

4 hours =  mint

No of times they will troll together in next 4 hours =  = 5 times