Question

a certain drug is made from only two ingredients: compound a and compound b. there are 3 milliliters of compound a used for every 2 milliliters of compound b. if a chemist wants to make 355 milliliters of the drug, how many milliliters of compound b are needed?

Explanation:

Step1: Set up ratio - proportion

The ratio of compound A to compound B is 3:2. Let the amount of compound B be $x$ milliliters. The total volume of the drug is 355 milliliters. The ratio of compound B to the total volume is based on the ratio of the components. The sum of the ratio parts is $3 + 2=5$.

Step2: Calculate amount of compound B

We know that the fraction of compound B in the total mixture is $\frac{2}{3 + 2}=\frac{2}{5}$. So, $x=\frac{2}{5}\times355$.
$x = 2\times\frac{355}{5}=2\times71 = 142$.

Answer:

142 milliliters