Question Find the quantity of compound A needed to make 648 milliliters of a drug, given that the drug is made from 5 milliliters of compound A for every 3 milliliters of compound B.
$\frac{5}{3}$ milliliters of compound A are used for every milliliter of the drug. To make 648 milliliters, the amount of compound A required is $\frac{5}{3} \times 648$ milliliters.