Amixture of 10% acid and 90% water is added to 5 liters of pure acid. the final mixture is 40% water. how many liters of water are in the final mixture?

The total amount of water, divided by the total amount of acid/water mixture is 40%. We then solve for the amount of mixture that we had prior to adding the 5 L of pure acid.

.9x / (x + 5L) = .4

.9x = .4x + 2 L

.5x = 2L

x = 4L

You started with 4 Liters of the mixture

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