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# 1.10 Composition of numbers: 11–19

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

## Introduction

Explore the ten-and-a-bit nature of the numbers 11–19, using the partitioning structure; apply number facts within ten to addition and subtraction of single-digit numbers to/from the numbers 11–19.

## Teaching points

• Teaching point 1: The digits in the numbers 11–19 tell us about their value.

• Teaching point 2: The numbers 11–19 can be formed by combining a ten and ones, and can be partitioned into a ten and ones.

• Teaching point 3: A number is even if the ones digit is even; it can be made from groups of two. A number is odd if the ones digit is odd; it can’t be made from groups of two.

• Teaching point 4: Doubling the numbers 6–9 (inclusive) gives an even teen number; halving an even teen number gives a number from six to nine (inclusive).

• Teaching point 5: Addition and subtraction facts within 10 can be applied to addition and subtraction within 20.

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