Question

1. to create a desired concentration, we must have 4mg substance for every 60 ml solution. how much substance is needed to make 100ml solution?

Explanation:

Step1: Set up proportion

Let $x$ be the amount of substance needed for 100 ml solution. The proportion is $\frac{4}{60}=\frac{x}{100}$.

Step2: Cross - multiply

$60x = 4\times100$.

Step3: Solve for $x$

$x=\frac{4\times100}{60}=\frac{400}{60}=\frac{20}{3}\approx6.67$ mg.

Answer:

$\frac{20}{3}$ mg or approximately $6.67$ mg