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.