3
Parts and wholes
Learner’s Book 1: Unit 5, pp. 81–82
GoalUse a part-whole diagram to take a part away from the whole and find what is left.
New words
whole · the big number we start withpart · one piece of the wholeleft over · the part that is still there
Explanation
A part-whole diagram helps us take away. The whole is the number we start with. To take away, we split the whole into two parts. One part is the number we take away. The other part is what is left over. For 6 take away 4, the whole is 6. Put 4 counters in the first part. Move the rest to the other part. There are 2. So 6 − 4 = 2. Before you start, make an estimate, a good guess. Then check it.
Worked examples
The whole is 7. We take away 4. What is left over is 3. 7 − 4 = 3.
The whole is 9. We take away 6. Cross out 6 stars and count: 3 are left over. 9 − 6 = 3.
Estimate first: 10 − 4 is about 6. Now jump back 4 from 10 on the number line. You land on 6. The estimate was right.
Class activity
Two-circle game: draw one big circle (the whole) and two small circles (the parts) on paper. Put 7 counters in the big circle. Move 3 into one part circle, and the rest into the other. Count the rest. Say: ‘7 take away 3 equals 4’. Try other wholes up to 10.
Practice
1
The whole is 7. Take away 5. How many are left?
2
2
8 − 2 = ?
6
3
9 − 7 = ?
2
4
6 − 5 = ?
1