8th grade
posted by Jake .
An alloy of metals is 25% copper .Another alloy is 50% copper. How much of each alloy should be used to make 1000grams of an alloy that is 45% copper?

.25(x)+.50(1000x)=.45(1000)
where x is the number of grams of 25% copper
and 1000x is the rest of the 1000 grams i.e. the number of grams of 50%