# Focus on Math

## Helping children become mathematicians!

### Strike it Out: a Primary Game from NRICH March 5, 2013

Filed under: Basic Facts,General Math,Parents,Primary Math Ideas & Problems — Focus on Math @ 12:06 pm
Tags: ,

One thing that I came across recently on the NRICH math website is an quick primary students’ game for practicing addition and subtraction with numbers to 20. On the particular webpage for “Strike it Out”, they offer a poster (a picture of which is posted here), a short video clip of the game, and a power point file all which give the instructions for the game.

I had each of my grade two math classes playing this game recently as a warm-up activity, and they loved it! The games go quickly for the most part – of course, some of the pairs of students were slower at the game, but those students were still engaged and trying their best.

The rules, simply, are these:
• Using a number line marked 0-20, one student begins by creating and recording an addition or subtraction equation, e.g., 4 + 10 = 14. On the number line he crosses out the 4 and 10 and circles the 14. His turn is over.
• The partner must now create a new addition or subtraction equation, but it must use the number 14 as one of the first two numbers, e.g., 14 – 6 = 8. She would crosses out the circled 14, crosses out the 6, and circles the 8. Her turn is over.
• The 8 must be used now by the first partner in his new equation, with the recording and crossing out and circling continuing.
• Play continues until one of the partners cannot make a correct number sentence, and the player who made the last correct equation wins.

Although there are many possibilities for equations near the beginning of the game, there are fewer possibilities as the game progresses. I watched students doing a lot of mental math trying to come up with appropriate equations. The students who needed support had a set of ten frames on the table to use to help the visualize and calculate.

I am including for download the game board page I made for students to use. (Cut the page in half to use.) Two students play on a single game board at a time.

There are lots of other great ideas on the NRICH math site for many different levels. I hope you will take some time and explore what is there!

Mathematically yours,
Carollee

Link to game on the NRICH math site here