The manager of a farmer's market has 450 lb of grain that costs $1.60 per pound. How many pounds of meal costing $0.80 per pound should be mixed with the 450 lb of grain to produce a mixture that costs $1.40 per pound?
Since we wish the mixture to cost 1.40 per pound be part grain (x) and part meal (1-x) we see that
x=.75. So then 75% of the mixture is grain and 25% is meal. Since there is 1/3 as much meal as there is grain (25%/75%=1/3) we need 450/3=150lbs of meal.