Question

Three bells toll at intervals of 9, 12 and 15 minutes. If they start tolling together,

after what time they will next toll together?

Answer 1

Explanation:

the least common multiple LCM.

this is created by the longest chains of the individual print factors of each number.

9 = 3×3

12 = 2×2×3

15 = 3×5

the longest chain for 2 is 2×2.

the longest chain for 3 is 3×3.

the longest chain for 5 is 5.

the LCM = 2×2×3×3×5 = 180

they will toll together again after 180 minutes = 3 hours.