# Starting our exploration of the decimal system with a card game

My daughter’s last day of School was on Friday. On Saturday, we started our Math journey. Just to show Rosie, sooner rather than later, that I will do my very best to make it enjoyable.

A deck of cards on the kitchen table did the trick.

Even if the card game, based on adding up pairs of numerals to make 10, was a subtle step towards our exploration of the decimal system, and its magic number 10 (i.e 10 digits, 0 to 9), the base number of our system of numeration . First, we explored the concept, then, we played.

Exploring…

Now, your child may already know by heart all pairs of numerals that make 10. But I was not sure about Rosie. Throughout the year, she brought home worksheets with equations balanced correctly (e.g. 4+6=10), but I wanted to check she understood what was underneath each symbol, each digit, each equation.

1) She first explored ways to make 10, on her own, using her beloved Legos®.

What I found interesting is that Rosie quickly mentioned that whether she started with 8 Legos® and completed with 2 Legos®, or started with 2 Legos®, and completed with 8 Legos®, she ended up with 10 Legos® . Away from any symbol, without knowing it, she was building up fondations of the commutative property of addition (e.g. 8 + 2 = 2 + 8).

2) Then, we added some symbols. And finished with the equation. This step is fundamental to me: connecting the numbers of Legos® (i.e. how many Legos® she had in front of her) to the numerals (i.e. the symbol representing the number of Legos®) of the equation.

3) Finally, we decided to take pictures of all her combinations. Another option would have been to draw the combinations.

No need to say that she was ready to play.

… and playing

I have never written card game rules before, so please, write a comment or contact me if you need some clarification. Fortunately, Buzz Lighter and Woody came to my rescue, allowing me to take pictures as they were playing.

Players and Cards

• The game is played by 2-4 people, with a deck of 40 cards (Ace,  2 to 10).
• The goal for the players is to get rid of all their cards in hand, by pairing cards so that the sum of their numerals equals 10 (e.g. an Ace with a Nine, a Eight with a Two, etc).

Rules

• All players receive 5 cards, displayed face up in front of them.
• The players look at their hands, and discard the pair(s) of cards making 10 (e.g. Buzz Lighter can make a pair with a Four and a Six. Woody cannot.)
• The first player draws a card from the  stock pile.
• If he/she can combine the card with one of his/her cards to make a 10, he/she withdraws both cards and plays again (e.g. Buzz Lighter draws an Seven and combine it with a Three to make a 10. He withdraws both cards).
• If he/she cannot , he/she just withdraws the card.
• It is the second player’s turn to play. And so on until one player gets rid of all his/her cards.

Playing with a rising 1st grader, I kept the rules quite basics on purpose, but here are some examples of modifications you could do with upper graders:

• Players can make 10 by combining several cards (e.g. a Two, a Five and a Three).
• When a player draws a card, he/she puts it on the table so that the card is available to anybody, i.e. the fastest player to see a pair, gets the card
• A player who cannot make a pair has to keep the card, i.e. the game goes longer, as each player can get more and more cards
• and… anything you may see that can add some enjoyment !

Have fun doing Math !