Question

Kelly heard two bells ringing together at 8:00 AM. The first bell rings after every 525 seconds, and the second bell rings after every 700 seconds. When will they ring together again?

• A. 8:45 AM
• B. 8:35 AM
• C. 9:25 AM
• D. 8:25 AM

Answer 1

The correct option is B 8:35 AM

The bells need to ring together at the next common time.
Therefore, we will have to find the LCM (least common multiple) of these numbers to know after what time both bells will ring together.

$\therefore \text{LCM of 525, 700}=5\times 5\times 7\times 3\times 4$
$=2100$

So, the bells will ring together after every 2100 seconds, i.e., $\frac{2100}{60}=35minutes.$

So, both the bells will ring together once again at 8:35 AM.