There are four table clocks. They ring every 10 min, 15 min, 20 min and 25 min respectively. If they all ring together at 10a.m., then at what time will they ring together again?

Correct option is C

Given:
Clock A rings every 10 minutes.

Clock B rings every 15 minutes.

Clock C rings every 20 minutes.

Clock D rings every 25 minutes.

All clocks ring together at 10 a.m.

Formula Used:

The clocks will ring together again after a time interval equal to the Least Common Multiple (LCM) of their intervals.

Solution:

Calculate the LCM of 10, 15, 20, and 25:

$$\text{LCM} = \text{LCM}(10, 15, 20, 25) = 300 \ minutes$$​​

Thus, all clocks will ring together again after 300 minutes.

Since they all rang together at 10 a.m., they will ring together again at 3:00 p.m..