## “Crossing the Decade” Concentration

This game is a version of the traditional memory or concentration game.

You will need to create a set of number cards for each of the pair of numbers that cross the decade, i.e., 19 and 20, 29 and 30, 39 and 40, 49 and 50, etc.

Students place all the number cards that end with “_9” face down in an 3x3 array on the left and all the number cards that end with “_0” face down in a 3x3 array on the right. Working in pairs or trios, students take turns. The first student selects a card from the left array, stating the number name and the counting number that follows (“I have 39, I need 40”).

He or she then picks one card from the array on the right (the “_0” numbers), hoping to find the target number. If the student does not find a pair, both cards are replaced face down in their original spots. It is now the second student's turn to choose a card from the “_9” array and to try to find the appropriate “_0” card. Students should try to remember where each number is located. (The game is called "Concentration" not "Guessing.")

When a student finds a matching pair he or she keeps that pair of cards. Play continues until all cards have been matched. The student with the most matched pairs wins.

## Comments

Log in to comment## Benti Dueck says:

over 4 yearsWe played this game on the carpet, whole class, for 3 days in a row. Then I put it in the 'Math Tub' to use during stations. The kids use it regularly.

## Jason says:

about 5 yearsI think this task could be cross-tagged to K.CC.1 as well.

## Kate Greeley says:

over 6 yearsThis activity would make a great math station. I will pass this along to my kindergarten teachers and first grade teachers!

I have played a similar game with students who need to practice this concept. Lay out 10, 20, 30, 40, 50 in a column and two place holder columns on either side of the decade number for the number before and the number after. Students draw a number from the pile and place it in the correct position. This activity is a bit more difficult because the child is going backward and forward. For some students it helps to scaffold by having a few examples already completed.

## Kristin says:

over 6 yearsThanks for your comment! Let us know how it works with your students and let us know if the task can be improved in any way.