If 5 machines can produce 60 pots working 10 hours a day, then how many pots can be made when 15 machines work for 30 hours a day?
More machines means more pots can be made, so it is in direct proportion. The proportion is 5:15∷60:x
If more hours spend, then more pots can be made, so it is in direct proportion. The proportion is 10:30∷60:x
We know that the product of extremes = the product of means.
5×10×x=15×60×30
x=(15×60×30)/(5×10)=3×6×30
=540