Year 1 Mathematics · AC9M1N05
Additive problems can involve joining, taking away, comparing or finding a missing part. Diagrams and materials help decide what to do
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Additive problems can involve joining, taking away, comparing or finding a missing part. Diagrams and materials help decide what to do.
Learning routine: Read story → Draw/model → Choose operation → Solve → Check answer
Think: 7 + ? = 10, so the change is 3c.
The diagram shows whether you are finding the total, a leftover, or a missing part.
Explain your thinking: Say what each part of the model represents, then explain why the answer or conclusion follows.
Cost 7c Pay 10c Change ?
start change result
Shop model Use play coins to solve a simple buying and change problem. Model: 10c − 6c = 4c
Bar model Draw parts and whole for an additive story. Model: part + part = whole
These curriculum examples extend the central model into varied contexts. They are learning contexts, not extra definitions to memorise.
modelling problems involving addition and subtraction presented in stories, using a Think Board to represent the problem, solving the problem using physical materials and explaining the connections between any materials used, the Think Board diagram and the numbers within the story
Try and explain: A box holds 13 crayons. Eight are blue and the rest are red. How many are red?
Five are red. Show a whole of 13 split into eight and the missing part; 13 − 8 = 5 or 8 + 5 = 13.
modelling simple money problems involving addition and subtraction using whole dollar amounts; for example, setting up a shop and role-playing practical problems of buying and selling of goods, using addition and subtraction with play money and prices in whole dollar amounts; solving the problem “I had \$14 and was given \$15 for my birthday” using addition to answer the problem
Try and explain: At a pretend shop, a notebook costs $6 and a pen costs $3. You pay $10. How much change is due?
The cost is $9, so the change is $1. Check that $9 + $1 equals the $10 paid.
modelling a variety of different additive situations to solve practical problems; for example, keeping track of the number of people on a bus as it stops to pick up and drop off passengers or the number of people entering a lift
Try and explain: A bus has nine passengers. Four get off and six get on. How many are on the bus now?
9 − 4 = 5, then 5 + 6 = 11 passengers. Account for both changes in the correct order.
Represent an additive problem, solve it and say what the answer means.
A game needs 15 counters. There are 9 on the table. How many more are needed?
Watch for this mistake: The words ‘more’ do not always mean add the two numbers given. Ask what is known and which part is missing.
A book costs $7. You pay with $10. How much change should you receive?
Find the missing part between 7 and 10.
$3. The $7 cost and $3 change together equal the $10 paid.
There are 8 red blocks and 5 blue blocks. Draw a model and find the total.
Both coloured groups are parts of one total.
13 blocks; 8 + 5 = 13.
Key idea: Additive problems can involve joining, taking away, comparing or finding a missing part. Diagrams and materials help decide what to do.
Return to the concept model if an answer is uncertain. Use the model to explain, not just to guess.
Use the Practice Sheet for written or hands-on work, Practice for supported feedback, and Test when the student is ready to demonstrate independent mastery.
Additive problems can involve joining, taking away, comparing or finding a missing part. Diagrams and materials help decide what to do.
Learning routine: Read story → Draw/model → Choose operation → Solve → Check answer
AC9M1N05: use mathematical modelling to solve practical problems involving additive situations including simple money transactions; represent the situations with diagrams, physical and virtual materials, and use calculation strategies to solve the problem
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