You have a stock solution that is 220 mg/mL and you need 10 mL of a working solution that is 43 mg/mL. What volume of stock solution will you need to dilute to have 10 mL of working solution at the above concentration?

The answer to your question is 2 ml

Explanation:

Data

Initial volume = ?

Initial concentration = 220 mg/ml

Final volume = 10 ml

Final concentration = 43 mg/ml

Equation

Initial volume x Initial concentration = Final volume x Final concentration

Solve for Initial volume

Initial volume = (Final volume x Final concentration) / Initial concentration

Substitution

Initial volume = (10 x 43) / 220

Simplification

Initial volume = 430 / 220

Result

Initial volume = 1.95 ml ≈ 2.0 ml