prepare 500 ml of a 1:5 solution using a 1:10 solution and a 1:4n solution. what quantities will be used of each stock solution to make the 1:5 solution?

Answer 1

500 ml of a 1:5 solution contains 500*(1/5)=100 ml. of the concentrate.
So if x is the volume of 1:4, then 500-x is the volume of 1:10.
Hence
x(1/4)+(500-x)(1/10)=500*(1/5)
Solve for x to get x=333.33 ml.

Answer 2

a chemist needs 130ml of a 75% solution but has only 67% and 80% solutions available. find how many milliliters of each that should be mixed to get the desired solution.