Question

Tilly the dog barks every 9 seconds.
Billy the dog barks every 12 seconds.
They both bark at the same time.
After how many seconds will they next bark at the same time?

Answer 1

useLCM

24 SEC is I think so

Answer 2

Lcm of 12,9=36 and next is 72

so 72-36=36 sec

after 36 second they will bark at same time