Question 362997
how much water must be mixed with 5 pints of a solution that is 90% developer to produce a mixture that is 39% developer?
.
Let x= amount (pints) of water added
then

.90(5) = .39(5+x)

4.5 = 1.95 + .39x
2.55 = .39x
6.54 pints = x (water to be added)