A fruit punch is made by mixing pineapple juice, orange juice, and lemonade in the ratio 1 : 3 : 6.

If 500 ml of pineapple juice is used, how much orange juice is needed?

The total ratio of the mixture is 1 + 3 + 6 = 10.

If 500 ml of pineapple juice is 1 part of the mixture, then:
3 parts of the mixture would require 3/1 x 500 ml = 1500 ml of orange juice.
Therefore, 1500 ml of orange juice is needed.

To find out how much orange juice is needed, we need to determine the ratio of pineapple juice to orange juice. Since the ratio of pineapple juice to orange juice to lemonade is 1 : 3 : 6, we know that the ratio of pineapple juice to orange juice is 1 : 3.

Therefore, if 500 ml of pineapple juice is used, we can calculate the amount of orange juice needed by setting up a proportion:

1 part pineapple juice / 3 parts orange juice = 500 ml / x

Cross-multiplying gives us:

1 * x = 3 * 500 ml

x = (3 * 500 ml) / 1

x = 1500 ml

Therefore, 1500 ml of orange juice is needed.