Question 259558
This is a mixture problem. Here is a chart based on the information. The thing to remember is that water is 0% fruit drink.
fluid . . . . . . . . % . . . . . . . . . .ounces . . . . . . . .. %*ounces
fruit . . . . . . . .90 . . . . . . .. . . . .10 . . . .. . . . . . .. 900
water . . . . . . .0 . . . . . .. . . . . ..  X . . . . .. . . . . . . .0
mixture . . . . . 50 . . . . . .. . . .. . 10+X . . .. . . . . . .500 + 50X
set 
900 + 0 = 500 + 50X
subtract 500 to get
400 = 50x
divide to get
8 = x.
It takes 8 ounces of water to get 50%.