The cards have been designed to be used in a class of 15 or 25 students. A symbol, at the bottom of the cards can be used to sort the cards. If you use cards with a ♡ the set will make one cycle with 25 cards. If you use cards with a ♧ the set will make a cycle of 15 cards. Using the symbols you can quickly sort the cards into a set of 15 or 25 cards.
Included in this activity are
1) A teacher’s master list of all 26 cards. The “I Have” for card 1 is not the answer to card 1. It is the answer to either card 15* or 25. The “I Have” for card 2 is the answer to card 1.
2) One set of 15 (♧) or 25 (♡) cards without number lines and
3) One set of 15 (♧) or 25 (♡) cards with number lines.
Distribute copies of the Student Recording Sheet for students to record their solutions to the cards as they are read.
You need to use either the set of 10 cards (♢), 15 cards (♧), 20 cards (♤) or 25 cards (♡) to complete a cycle. In one lesson you might use the cards without number lines. Another time you might use the cards with the number lines. Another time you might mix the cards by having some with graphs and others without. The cards have been designed to give you some options for putting the lesson together.
One set of cards has number lines because this could help students reason their answer from the number line. Since subtraction does answer the question of the space between the two numbers a number line could help students notice that (-1) - (+3) and (+1) - (-3) have similar answers. In
(-1) - (+3)= -4 the larger number is being subtracted from the smaller number the answer is negative. In (+1) - (-3)=+4 since the smaller number is being subtracted from the larger number the answer is positive.
Distribute the cards (15 (♧) or 25 (♡)). Have anyone read their question for “Who Has”. The rest of the students should set up problem and try to solve it. When someone discovers they have the answer to the question, they read their card. This produces a new card and a new problem. The new problem is described and the class works on new problem. This procedure continues until the last person reads their problem and it turns out to be the answer of the original first card.
In the solutions to the questions, the subtraction problems are changed to addition of the opposite number and then the addition property of zero in used to simplify each answer.