Purpose

The purpose of this activity is to help students learn groupings within 20. For example 12 and 8 make 20; 16 and 4 make 20.

Achievement Objectives

NA1-3: Know groupings with five, within ten, and with ten.

Specific Learning Outcomes

recall groupings within 20. For example 12 and 8 make 20; 16 and 4 make 20.

Required Resource Materials

Calculators

Activity

- Show the students how to make the calculator show pieces of 20. Do this by pressing the keys: “20 – 20 =”. Then, when any number less than 20 is entered, followed by the equals key, the calculator will display the remaining “piece” of twenty. For example, if “5 =” is entered, the calculator will display “15”. (Note that the result is displayed as a negative number, but this can be disregarded.)
- Enter the number “12” into the calculator and say:
*We have put the number 12 into the calculator. When we press the “=” key it will show us the remaining piece of twenty. What will that be?* - Once students have given their answers, show them that the answer from the calculator is 8.
- Continue as a whole group in this way, or have students work in pairs with one student entering the numbers into the calculator and the other identifying the “missing piece” of 20.

### Additional Activity

This activity can be repeated in a similar way to help learn groupings within 10.