Question

Two gongs strike at intervals of 16 and 20minutes respectively. At twist time will they strike together again if they start simultaneously at 12 noon? Hint: 60 minutes = 1 hour

Answer 1

1:20 pm

Explanation:

The both strike at noon.

Gong 1 strikes every 20 minutes, gong 2 strikes every 16 minutes. Try to multiply each by a number so you get the same result. The number you multiply each by will be different, but the final product will be the same.

For example:

take 20 and multiply by 4 to get 80,

now take 16 and multiply it by 5 to get 80.

So in 80 minutes, gong 1 will strike 4 more times, and gong 2 will strike 5 more times, and at 80 minutes, they will both strike again.

This is the soonest this will happen, since no numbers less than 4 or 5 will make the product of these numbers equal.

80 minutes is 1 hr and 20 minutes, so 1:20 pm is the next time they strike together