Pierre was trying to sleep one night but there was too much noise around him. His clock ticked every 18 seconds, a tap was dripping every 25 seconds and his dog snored every 20 seconds. He noticed on his clock that all 3 things happened together at 8 p.m.
- At what time would all 3 things happen together again?
- How many times would all 3 things happen together again from 8 p.m. to 9 p.m.?
(a)
LCM of 18, 25 and 20 = 900
1 min = 60 s
900 s = 900 ÷ 60 = 15 min
15 min after 8 p.m. is 8:15 p.m.
(b)
From 8 p.m. to 9 p.m. = 1 h
1 h = 60 min
Number of times all 3 things happened together
= 60 ÷ 15
= 4 times
Answer(s): (a) 8:15 p.m.; (b) 4