Question

A bell rings every 30 seconds, and another bell rings every 50 seconds. If they ring simultaneously now, after how many seconds will they ring simultaneously again?

• A. 1500
• B. 300
• C. 150

Answer 1

The correct option is B 300

To find out at what time the two bells will ring together, we must find the LCM of 60 seconds and 50 seconds.

Prime factorizations of 60 and 50 are

60 = 2 × 2 × 3 × 5
50 = 2 × 5 × 5

LCM is the product of maximum occurrences of each prime factor in the given numbers.

So LCM (30, 50) = 2 × 2 × 3 × 5 × 5 = 300 seconds
Hence, the bells will ring after 300 seconds.