If eleven plus two equals one, what does nine plus five equal?

What has to be broken before you can use it?

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

The doctor prescribed you to take one pill from the bottle every half an hour. The bottle is now left with only three pills.

How long do you think you have before you run out of pills?

what does the below math rebus puzzle mean?

Different lights make me strange by changing me into different sizes. What am I?

There is something which you can be arrested for attempting but not for successfully completing.

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

If I put in one bird per cage, I have one bird too many. If I put in two bird per cage, I have one cage too many. How many cages and birds do I have?

When does a USA Potato change its nationality?