10th Class Mathematics Real Numbers Question Bank MCQs - Real Number

Four bells toll at intervals of 10 s, 15 s, 20 s and 30 s respectively. If they toll together at 10: 00 am at what time will they toll together for the first time after 10am?

A) 10: 01 am

B) 10: 02 am

C) 10: 00: 30 am

D) 10: 00: 45 am

Correct Answer: A

Solution :

The time interval between simultaneous tolling of the bells = LCM (10 15 20 30) s

= 60 s = 1 min

Hence the bells will toll together again for the first time after 10: 00 am at 10: 01 am.