Question

A chemist mixes a 10% hydrogen peroxide solution with a 25% hydrogen peroxide solution to create 30 liters of a 15% hydrogen peroxide solution. How many liters of the 10% solution did the chemist use to make the 15% solution?
liters

Answer 1

Answer:

let x be the number of liters for the 10% solution

let y be the number of liters for the 25% solution

:

total liters for 10% solution is 0.10x

total liters for 25% solution is 0.25y

:

x + y = 30

total liters of 15% solution is 0.15 * 30 = 4.50 liters

:

y = 30 - x

:

0.10x + 0.25(30-x) = 4.50

:

Note that I substituted for y for the 25% solution

:

0.10x + 7.50 -0.25x = 4.50

:

-0.15x = -3.00

:

x = 20