Question

How many ml of 1:4 solution and how many ml of sterile water are needed to prepare 600 ml of 1:20 solution ?

Answer 1

Approximately 143 mL of 1:4 solution and 457 mL of water

Explanation:

A 1:4 solution has a concentration of 1/(1+4) = 1/5 or 20%.

Similarly, a 1:20 solution has a concentration of 1/(1+20) = 1/21 or 4.76%.

If x is the mL of 20% solution and y is the mL of water, then:

x + y = 600

1/5 x = 1/21 (600)

Solve:

x = 5/21 (600)

x ≈ 143

y ≈ 457

You need approximately 143 mL of 1:4 solution and 457 mL of water.