# Three bells toll at intervals of 9,12 and 15 minutes respectively

Three bells toll at intervals of 9,12 and 15 minutes respectively. All the three begin to toll at 9 a.m. At what time will they again toll together?

(a) 11.30 a.m.

(b) 11.45 a.m.

(c) 12.00 noon

(d) 11.20 a.m.

**Answer: (c) 12.00 noon **

**Solution:-**

The factors of 9 = 3 x 3

The factors of 12 = 2 x 2 x 3

The factors of 15 = 3 x 5

Then, the L C M of 9, 12 and 15 = 2 x 2 x 3 x 3 x 5

= 180

So, after 180 minutes the bell toll together.

Then, time will be 9 a. m. + 180/60 hours

= 9 a. m. + 3 hours

= 12 noon.

Hence, the correct answer is option (c) 12.00 noon.