Multiple Ways to Add and Subtract

Purpose

These exercises and activities are for students to use independently of the teacher to practise number properties.

Achievement Objectives

NA4-1: Use a range of multiplicative strategies when operating on whole numbers.

AO elaboration and other teaching resources

Specific Learning Outcomes

use common factors to help solve addition and subtraction problems

Description of Mathematics

Addition and Subtraction, AM (Stage 7)

Required Resource Materials

Homework with answers (PDF or Word)

Practice exercises with answers (PDF or Word)

Activity

Prior knowledge

Recall multiplication basic facts

Know factors

Familiarisation with the use of brackets in notation

Multiply two digit numbers by a single digit number using the distributive law
eg 15 x 6 = (10 x 6) + (5 x 6) = 90

Background

The strategy in this activity involves finding a common factor of numbers in an addition problem. For example, 27 + 45 a common factor of 27 and 45 is 9. So 27 + 45 = (3 x 9) + (5 x 9). Then by using the distributive property the equation can be rearranged as 27 + 45 = (3 x 9) + (5 x 9) = 8 x 9 = 72.