Quote:

The King took a cup filled with juice and drank $\displaystyle \tfrac{1}{5}$ of its contents.

When the king looked away, the Jester refilled the cup by adding water.

The King drank $\displaystyle \tfrac{1}{4}$ of this mixture.

Again the Jester refilled the cup with more water.

The King drank $\displaystyle \tfrac{1}{3}$ of this mixture.

The king looked away, and the Jester refilled the cup with water.

What percentage of this final mixture was water?

This problem has to be explained to elementary school age children.

They have no algebra concepts.

It can be done or it would not have been asked of me.