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# 1.9 Composition of numbers: 20–100

Created on 31 July 2017 by ncetm_administrator
Updated on 16 January 2018 by ncetm_administrator

## Introduction

Build on multiples of ten, by introducing non-zero values in the ones place; apply the partitioning structure to these two-digit numbers, decomposing them into tens and ones.

## Teaching points

• Teaching point 1: There is a set counting sequence for counting to 100 and beyond.

• Teaching point 2: Objects can be counted efficiently by making groups of ten. The digits in the numbers 20–99 tell us about their value.

• Teaching point 3: Each number on the 0–100 number line has a unique position.

• Teaching point 4: The relative size of two two-digit numbers can be determined by first examining the tens digits and then, if necessary, examining the ones digits, with reference to the cardinal or ordinal value of the numbers.

• Teaching point 5: Each two-digit number can be partitioned into a tens part and a ones part.

• Teaching point 6: The tens and ones structure of two-digit numbers can be used to support additive calculation.

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