Numbers and Operations Number of players: 3 Materials: Index cards

How Do You Stack Up?

Make three sets of cards containing the numbers shown below. (The numbers in parentheses tell how many cards to make for each number.) Shuffle the cards and put them in a pile. Sit in a circle on the floor.

Each group member takes five cards. These cards show the prime factors of a number. Each group member writes the product of the prime factors on a sheet of paper. Then one group member places his or her cards face up in a single row and arranges them so that the factors are in increasing order. Each of the other two group members place any cards showing the same factors face up on top of the first group member's cards. Find the product of the numbers on cards for which there is more than one card in the stack. This is the GCF of the numbers each group member wrote. Show the number you wrote to the other group members.

Repeat the procedure several times, shuffling all the cards each time.