Question

A tank contains 8000 litres of solution that is 40 percent acid. how much water should be added to the solution to make a solution that is 30 percent acid​

Answer 1

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40% of 8000 = amount of acid or 3200 liters of acid.

8000-3200 = 4800 so we've got 4800 liters of water.

w +a = solution

4800 + 3200 = 8000

must add 'x' amount of water:

(4800 + x) +3200 = 8000 + x

30% of new solution is acid

30% of (8000 +x) = amount of acid

.3(8000+x)= amount of acid

2400 + .3x = amount of acid

but amount of acid didn't change, it's still 3200 liters

3200 = 2400 + .3x

800= .3x

800/.3= x

2666.67 = x = amount of water to add.