After woking in West Vancouver yesterday, introducing addition and subtraction of decimal numbers to Grade 4 students, I was encouraged to edit a game originally designed for basic place value in primary to be applicable to decimals (to tenths).
You can download the Closest to 10.0 – decimal game instructions and game cards here.
The idea is that students choose 2 decimal numbers from the set that will get them closest to 10.0 when added together. The closer sum wins, and play continues until all the cards are used up.
The more interesting tool to accompany this game is the Decimal “Hundreds” Chart. Although there are indeed 100 numerals on the chart, they largest is 10.0, not 100. The purpose of this tool is to explore patterns in increasing decimal numbers, and to explore adding and subtracting whole numbers and tenths. Have students place a counter on 0.1, then roll a die with the following faces:
+ 1.0, +1.0, -1.0, +0.1, +o.1 and -0.1
With each roll, students move their counter according to the instructions, racing against a partner to “Get to 10.0”. It’s a simple game, but reinforces what happens when we increase or decrease a number by tenths and whole numbers. Once students are familiar with this pattern (down a row is like adding 1.0, to the left one is like subtracting 0.1… etc.) they can use the hundreds chart to add larger numbers and to find the difference between decimal numbers (ie: adding 2.3 is like moving down 2 rows then to the right 3…).