Explore the connection between addition and subtraction (ACMNA029)

 

• use concrete materials to model how addition and subtraction are inverse operations

• use related addition and subtraction number facts to at least 20, eg 15 + 3 = 18, so 18 – 3 = 15 and        18 – 15 = 3

 

Video showing how

addition and subtraction relate

 

Inverse Addition/ Subtraction

(scroll to bottom of page for activity)

 

Triangular Cards

 

Cross the Swamp

 

 

Solve simple addition and subtraction problems using a range of efficient mental and written strategies (ACMNA030)

 

• use and record a range of mental strategies to solve addition and subtraction problems involving two-digit numbers, including:

− the jump strategy on an empty number line

− the split strategy, eg record how the answer to 37 + 45 was obtained using the split strategy

    30+40=70    7+5=12    so 70+12=8

− an inverse strategy to change a subtraction into an addition, eg 54 – 38: start at 38, adding 2 makes 40, then adding 10 makes 50, then adding 4 makes 54, and so the answer is 2 + 10 + 4 = 16

 

Interactive Abacus

(use for demonstrating strategies)

 

Interactive Number Line

(demonstrate strategies)

 

Addition (Split Strategy)

 

Addition with 10s on a Number Line

(Jump Strategy)

 

Missing Numbers (Inverse Strategy)

 

The following games can be used to demonstrate a range of strategies -

 

Techno Tortoise  (Jump Strategy)

 

Addition and Subtraction

(hover at top of page to choose activity)

(Jump Strategy)

 

Aztek Take Away

 

Count on Convict

(explore addition patterns to find subtraction)

 

Bricks Addition/ Subtraction Games

 

 

• select and use a variety of strategies to solve addition and subtraction problems involving one- and two-digit numbers

    * perform simple calculations with money, eg buying items from a class shop and giving change (Problem Solving)

 

IXL Money

 

Money Master

(has wide range of currencies)

 

Change Maker

(US Money but has numbers)

 

How Much Change

 

Price Lists – What 2/3 Things

(UK Money)

 

Give Chage (UK Money)

 

    * check solutions using a different strategy (Problem Solving)

    * recognise which strategies are more efficient and explain why (Communicating, Reasoning)

    * explain or demonstrate how an answer was obtained for addition and subtraction problems,

      eg show how the answer to 15 + 8 was obtained using a jump strategy on an empty number line

      (Communicating, Reasoning)