Question 51377
3parts natural oil for every 5 parts of synthetic oil. How many liters of Petrolyn oil can be made from 400 liters of synthetic oil? 
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[3 natural]/[5 synthetic] = [x petrol]/ [400 synthetic]

3/5 = x/400
Multiply both sides by 400 to get;
x=(3/5)400
x=3*80
x=240 liters of Petrol oil
Cheers,
Stan H.