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

| 4 Bells toll together at 11:00 A.M. They toll after 7, 8, 10 and 18 seconds respectively. How many times will they toll together again in the next 4 hours?

A. 3

B. 4

C. 5

D. 6

### Right Answer is: C

#### 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

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