Adnan K. answered 01/12/16
Tutor
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UM Grad for Physics , Math and Computer tutoring
It's simple
Let's see another example. Say you are driving a car at 50 miles per hour. So in 3 hours you will drive 50*3=150 miles
So if I ask, you can drive 150 miles in 3 hours, so how many miles can you drive in 1 hr? Simple. 150/3 =50 miles
Your question is same as my example. The factory produces 300 disks in 15 mins, so it produces 300/15 =20 disks in 1 min.
Cheers.