Answer
7.5 ounces of concentrate are needed
Work Step by Step
(Note: x:y is same as $\frac{x}{y}$)
Given:
3 ounces of concentrate are mixed with 2 gallons of water.
Thus ratio of concentrate to water = 3:2
Let new amount of concentrate be x ounces.
Given that 'x' ounces are mixed with 5 gallons of water.
Thus ratio of concentrate to water = x:5
Since the ratios are equal, $\frac{3}{2}$ = $\frac{x}{5}$
Cross multiplying, 2x =15, x = $\frac{15}{2}$
Thus x = 7.5 ounces of concentrate
