Question

A factory produces 12000 plastic bottles by using 3 machines 8 hours a day. One machine is out of order now. The owner wants to produce 15000 plastic bottles, How many hours the remaining machines have to work to produce the required bottles?

Answer 1

3 machines take 8 hours to do 12000 bottles
1 machine takes 24 hours to do 12000 bottle
2 machines take 12 hrs to do 12000 bottles
15000/12000 = 5/4 <--- should take 5/4 times as long
so 2 machines take (12)(5/4) hrs to do 15000 bottles
time taken = 15 hrs

check my arithmetic