Counting Back

Achievement Objectives
Specific Learning Outcomes

Solve subtraction problems to 100 by counting back in their heads.

Description of Mathematics

Number Framework Stage 4

Required Resource Materials
A set of small cards or tiles labelled 1 to 20.
Activity

Problem: Michelle has 11 sweets and eats 4. How many are left?

Record 11 - 4 on the board. Model the 11 sweets with tiles labelled in order 1 to 11.

Ask which 4 sweets would Michelle eat and how many will be left. The students need to connect with the idea that removing sweets 1 to 4 does not solve the problem but removing sweets 11, 10, 9 then 8 does because the set 1 to 7 remains. Complete 11 - 4 = 7 on the board.

Examples. Encourage students to track on their fingers which sweets get eaten using word stories and recording for: 13 – 4, 9 – 2, 19 – 3, 12 – 4, 11 - 5, 9 – 3, 12 - 4....

Using Imaging  and Imaging Only:

Shielding and Imaging Only: Examples. Word stories and recording for: 12 – 3, 19 – 2, 17 - 3 , 8 – 2, 21 – 4, 15 - 5....

Using Number Properties

Examples. 81 – 2, 90 – 2, 78 – 3, 62 – 4, 92 - 4....


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