How many oranges are needed to make 13 glasses of juice?

a. 6 1/2 oranges

b. 8 2/3 oranges

c. 9 oranges

d. 11 oranges

e. other

Reason:

1. The number of oranges compared to the number of glasses will always be in the ratio of 2 to 3

2. If there are seven more glasses, then five more oranges are needed.

3. The difference in the numbers will always be two.

4. The number of oranges will always be half the number of glasses.

5. There is no way of predicting the number of oranges.