- If it is blue, it is round.
- If it is square it is red.
- It is white or yellow.
- If it is yellow, it is square.
- It is square or round.
What conclusion can we draw?
We know that it is white or yellow and that it is square or round. As we know that if it is square it is red and cannot be red, it must be round.
They tell us that if it is yellow it is square, so it cannot be yellow, because we know it is round. Therefore, it must be white.
In short, whatever it is, it's white and round.