Question

a scientist needs 10 liters of a 20% acid solution for an experiment, but she only has a 5% solution and a 40% solution. To the nearest tenth of a liter, about how many liters of the 5% solution and the 40% solutions should she mix to get the solution she needs?

Answer 1

10 * .20 = .05 x + .40 ( 10-x)

5.7 liters of 5%

4.3 of the 40 %

Explanation:

we need 10 liter of a 20 % solution

We have x liters of 5% and since there is a total of 10 liters we have 10-x of the 40 % solutions

10 * .20 = .05 x + .40 ( 10-x)

2 = .05x +4 - .4x

Combine like terms

2 = 4- .35x

Subtract 4 from each side

2-4 = -.35x

-2 = -.35x

Divide by -.35

-2/.-35 =x

40/7 =x

5.7 =x

10 -5 5/7 = 4 2/7

4.3 of the 40 %