Question

A lab technician needs 35 ml of 15% base solution for a certain experiment,

but she has only 10% solution and 20% solution. How many milliliters of
the 10% and the 20% solutions should she mix to get what she needs?

Answer 1

17.5ml- of 10 percent solution, 17.5ml- of 20 percent solution

Explanation:

35:100*15=5.25- ml of alkali in the base solution

Suppose we need x ml of 10 percents solution and 35-x - of 20 percents.

Then The quantity of alkali in the first one (10 percents) is x/100*10=0.1x

when in the second one we have (35-x)/100*20= 7-0.2x of alkali

0.1x+7-0.2x=5.25

7-0.1x= 5.25

0.1x=1.75

x=17.5- 0f 10 percents

35-17.5=17.5 - of 20 percents