This adaptation of the card game Twenty-Five provides practice adding and subtracting positive and negative integers.
integers, positive, negative, numbers, addition, subtraction, game, card game
This card game is a variation of another teacher-submitted card game called Twenty-Five. That game involves simple addition and subtraction of whole numbers and can be played by students of any age. This game requires students to add and subtract positive and negative integers.
Arrange students into groups of two or more. Have students deal out as many cards as possible from a deck of cards, so that each student has an equal number of cards. Put aside any extra cards.
Explain to students that every black card in their pile represents a positive number. Every red cards represents a negative number. In other words a black seven is worth +7 (seven), a red three is worth 3 (negative 3).
Note: If this game is new to students, you might want to discard the face cards prior to dealing. If students are familiar with the game, or if you want to provide an extra challenge, leave the aces and face cards in the deck. In that case, explain to students that aces have a value of 1, jacks have a value of 11, queens have a value of 12, and kings have a value of 13.
At the start of the game, have each player place his or her cards in a stack, face down. Then ask the player to the right of the dealer to turn up one card and say the number on the card.
For example, if the player turns up a black eight, he or she says 8.
Continue from one player to the next in a clockwise direction. The second player turns up a card, adds it to the first card, and says the sum of the two cards aloud.
For example, if the card is a red 9, which has a value of -9, the player says 8 + (-9) = (-1)
The next player takes the top card from his or her pile, adds it to the first two cards, and says the sum.
For example, if the card is a black 2, which has a value of +2, the player says (-1) + 2 = 1.
The game continues until someone shows a card that, when added to the stack, results in a sum of exactly 25.
Extra Challenging Version
To add another dimension to the game, you might have students always use subtraction. Doing that will reinforce the skill of subtracting negative integers.
For example, if player #1 plays a red 5 (-5) and player #2 plays a black 8 (+8), the difference is -13: (-5) - (+8) = -13
If the next player plays a red 4, the difference is -9: (-13) - (-4) = -9. [Recall: Minus a minus number is equivalent to adding that number.]
Adapting for Special Students
For students who find the game too challenging, you might change the sum you're aiming for to a number less than 25. The game will end more quickly. As students become more comfortable with the game, you can gradually increase the numeric goal.
Observe student play. Support students who are having difficulty. After the game ends, have students write about it in their math journals; they might explain the rules in their own words, for example.
Pam Harper, Rockville Jr/Sr High School, Rockville, Indiana