juice is in the ratio of 2 parts concentrate to 1 part water. I have 9 gallons of juice. how much water must be added to make the juice in the ratio of 1 part water

You would need 4.5 gallons of water.

Step-by-step explanation:

To find this create a proportion. On the right, use the give ratio. On the left give the amount in the current mixture.

2/1 = 9/x

Now cross multiply to solve.

1 * 9 = 2 * x

9 = 2x

4.5 = x