Question

a machine takes 2.8 hours to make 9 parts. At this rate, how many parts can the machine make in 28.0 hours?

Answer 1

90 is your answer!!!

Answer 2

We can do 28 hours / 2.8 hours to find how many 2.8 hours go into 28 hours.

28 / 2.8 = 10

Which means we can multiple 9 by 10 = 90

So 90 parts in 28 hours

You can use ratios
( 2.8 : 9 )* 10
28 : 90

Hope it helps.