# Family Maths Thanks to everyone who took part in the two Family Maths Events on 21st Spetember, 2010. We had a wonderful time and, hopefully, learned a bit!

Maths Cards

Maths cards are simply a deck of the playing cards with the jokers and face cards removed, leaving only the aces (which count as a number 1) and the number cards. The remaining 40 cards in the deck are used in a variety of ways for a variety of games.

Maths Memory

Shuffle the 40 cards and lay them all out individually face down on a table or on the floor. Players take turns turning over two cards. If the pair of cards equals 10 (say, a 2 and an 8), the player keeps this set and takes another go. If the cards turned over do not add to 10, the player turns them back over and it is the next player’s turn. If a player turns over a 10 he or she does not turn over a second card. Instead that player keeps the 10 and has another go. If a player turns over a 10 as the second card in that turn, the total will be more than 10 and that player’s turn is over. In addition to helping with addition to 10, this game also helps to improve your child’s memory as he or she must remember where useful cards were located on the table or floor!

Number War

There are a number of variations to Number War. For Addition War, the deck is divided evenly among two players who keep their cards in a stack face down. At the start of each turn, each player turns over the top two cards which are added together. The player with the largest sum wins that round. For example, if player A turns over a 5 and a 3, her total is 8. Player B turns over an ace (which counts as a 1) and a 4, making a total of 5. In this round, player A is the winner. In the event of a tie, each player puts the first two cards to the side and turns over two more to find a new total. Assuming that the new cards do not lead to another tie, the player with the highest total wins all of the cards used in that turn. Addition War continues until one player holds the entire deck of cards. The game can be made a bit more difficult by turning over three cards at a time instead of two.

For Subtraction War by each player subtracts the lowest card from the highest and getting an answer. Again, the highest total wins each round. For example, if player A turns over a 5 and a 3, her total is 2 (5 – 3 = 2). Player B turns over an ace (which counts as a 1) and a 4, making a total of 3 (4 – 1 = 3). In this round, player B is the winner.

In Multiplication War, each player multiplies his or her two cards and getting an answer. Again, the highest total wins each round. For example, if player A turns over a 5 and a 3, her answer is 15. Player B turns over an ace (which counts as a 1) and a 4, giving a product of 4. In this round, player A is the winner. To make it more difficult, try using three cards at a time instead of two.

The basics of each of these Number War games can be used when your child starts to learn about negative numbers. By making the black cards represent positive numbers and the red cards negative numbers, you have three excellent games to play to help reinforce the basic operations using negatives.

Imagine that Player A turns over a red 3 and a black 6. Player B turns over a red 7 and a red Ace (or 1). Here is how those cards work in Negative Number Wars:

- Negative Addition: Player A’s cards become -3 + 6 (or 6 + -3) which equals 3. Player B’s cards become -7 + -1 (or -1 + -7) which equals -8, so Player A wins this round. Note that the order in which the cards are added does not matter to the total.

- Negative Subtraction: This time, the order the cards are subtracted does matter. It is up the each player to choose the best way to subtract his or her cards (see the Appendix for notes on negative numbers). Player A’s cards could be:

-3 - 6 = -9 or

6 - -3 = 9.

Player B’s cards could be

-7 - -1 = -6 or

-1 - -7 = 6

In this round, assuming that Player A chose the better of the two possible options, Player A would win.

- Negative Multiplication: As with Negative Addition War, the order in which the cards are multiplied does not make a difference to the total. So, Player A’s cards become -3 x 6 = -18 and Player B’s cards become -7 x -1 = 7 so Player A is the winner.

To combine all of the operations, try playing Wild War. In this variation, players turn over two cards and use whatever operation will give them the highest total. To make it more difficult, turn over three cards each turn and use more than one operation.