Posted by shelly on .
A movie theater runs two films continuously. One film runs for 85 minutes and a second film runs for 100 minutes. Both movies begin at noon. When will the two films start again at the same time?

math 
Reiny,
This is just like finding the LCM of 85 and 100
85 = 5x17
100 = 5x20
LCM = 5x17x20 = 1700
e.g.
85 170 255 ... 1615 1700 ...
100 200 300 .. 1600 1700 ..
It will take 1700 minutes = 28 hrs. 20 minutes.
Add that time to your noon.