This puzzle is a test of your logical reasoning.
You are presented with four cards which are on a table, such that you can only see the uppermost side. On the sides of the four cards you can see a black square, a circle, a side that is completely red and a side that is completely yellow.
You are told that every card has a shape on one side and the other side is completely one colour. Further, you are told that there is one rule that should be followed: if the card has circle on one side the other side must be completely yellow.
How many cards do you need to turn over, and which cards, in order to verify that the rule has not been broken?
You need to turn over two cards - the circle and the red.
You can ignore the square, as the rule says nothing about squares.
You must turn over the circle to check that the other side is yellow.
You can ignore the yellow card, as the shape on the other side doesn't matter. The rule doesn't say yellow must be paired with a circle.
You must turn over the read card to ensure that there isn't a circle on the other side.