Math
posted by Britney .
A family is moving and has a number of electronic devices in the same packing crate. One of the devices beeps every 8 minutes, another device beeps every 10 minutes, and a third device beeps every 12 minutes. If all the devices beeped together at 3:00pm, what time will they all beep together next?

What is the LCM for 8, 10 , and 12 ?

LCM, not GCF

Not sure, 120?

Right. So what's 120 minutes from 3:00?

first device: 8 16 24 .... 120
2nd device : 10 20 30 ... 120
3rd device: 12 24 36 ... 120
so 120 minutes from now they coincide
120 min = 2 hours
so at 5:00 all 3 will peep at the same time 
thank you!