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Level Three > Number and Algebra

Problems Like 73 – 19

Keywords:
Achievement Objectives:

Achievement Objective: Use a range of additive and simple multiplicative strategies with whole numbers, fractions, decimals, and percentages.

Purpose: 

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

Specific Learning Outcomes: 

solve addition and subtraction problems by compensating with tidy numbers

 

Description of mathematics: 

Addition and subtraction, AA (Stage 6)

Required Resource Materials: 
Practice exercises with answers (PDF or Word)
Activity: 

Prior knowledge

Addition basic facts

Background

This activity uses the mental strategy of compensating with tidy numbers. To subtract 18 from a number it is easier to subtract 20 and then add on 2.  The activity also use algebra to show the principle of subtracting a number then adding on a small number.

Comments on the Exercises

Exercise 1
Asks students to complete equations that show compensating with tidy numbers, e.g. 26 - 18 = 26 - 20 + 
 
Exercise 2
Asks students if equations that show compensating with tidy numbers are true or false.
 
Exercise 3
Asks students to complete equations by working what larger number is subtracted before the compensation is made.  Although the larger number is not necessarily a tidy number in these examples.
 
Exercise 4
Asks students to solve subtrction problems by using compensation and with tidy numbers.
 
Exercise 5 and 6
Asks students to generalise the principle of compensating wiht tidy numbers by using letter symbols in the equations.

 

 

Related Resources: 

Book 5: Problems Like 73 – 19 = ?.

AttachmentSize
ProblemsLike73-19.pdf96.56 KB
ProblemsLike73-19.doc47 KB

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