The ratio of compound A to compound B is 3:4, which means that for every 3 milliliters of compound A used, 4 milliliters of compound B are used.
To find out how many milliliters of compound B are needed to make 427 milliliters of the drug, we can use the proportion:
3/4 = x/427
where x is the number of milliliters of compound B needed.
To solve for x, we can cross-multiply and simplify:
3 x 427 = 4 x
1281 = 4x
x = 1281/4
x = 320.25
Therefore, 320.25 milliliters of compound B are needed to make 427 milliliters of the drug.