This tennis court is an addition mat. It is used in early childhood classrooms to demonstrate the concept of addition. It can also be used to demonstrate the concept of subtraction. For example:
How many tennis balls do we have all together? We need to count how many there are. There are one two three four five tennis balls. What if we take away three tennis balls, one two three. How many do we have left? One two.
How many tennis balls can you see? One two three four five six. What if three balls roll away? How many can you see? One two three. How many have rolled away? One two three. How many are left on the court? We count back from six. Six five four three. Later on we can use the doubles strategy, as we will know that double three is six, therefore three take away three is three.
Finally, say I want to have ten tennis balls and I only have seven, how many would i need to have seven tennis balls? We would think addition and count on until ten. starting at seven, counting on eight nine ten. How many more did we need. One two three tennis balls. The answer would be three.