Here is the information we know about this game:

• There are five red cards numbered, 1, 3, 5, 9 or 12. Each number is used exactly once.
• There are four numbered blue cards, 1, 3, 4 or 5. Each number is used exactly once.
• You withdraw a red card and a blue card. If the product of the two numbers obtained is a perfect square, you have removed a winning pair. What is the probability of drawing a winning pair?

A perfect square is an integer which can be expressed as the product of two identical whole numbers. 25 is a perfect square since it can be expressed as the product 5 × 5 or 5 2.