Achemist needs 30 liters of 25% acid solution. she has containers of 10% solution and 30% solution.

how many liters of each should she combine to get the needed solution?

if necessary, express your answer in decimals, and round to the nearest tenth.

x = amount (in liters) of the 10% solution she should use

y = amount of the 30% solution she should use

She wants a 30L solution, so

x + y = 30

Each liter of the 10% solution contributes 0.1x liters of acid, and each liter of the 30% solution contributes 0.3y liters of acid. 30L of 25% acid solution contains 30L*0.25 = 7.5L of acid, so

0.1x + 0.3y = 7.5

Now solve for x and y:

x + y = 30  ==>  y = 30 - x

0.1x + 0.3y = 7.5  ==>  0.1x + 0.3(30 - x) = 7.5

...  ==>  0.1x + 9 - 0.3x = 7.5

...  ==>  1.5 = 0.2x

...  ==>  x = 7.5  ==>  y = 22.5

4th option is correct xy=-10

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step-by-step explanation: