Short Blocks

# Maths Year 3 Autumn Addition and Subtraction (A)

Each unit has everything you need to teach a set of related skills and concepts.

## Unit 1 Number facts and inverse operations (suggested as 2 days)

### Planning and Activities

Day 1 Teaching
Use different sets of objects, including pegs on a coat hanger, to partition 12 into 2 sets. Then use bar diagrams and write 4 sentences. Learn the facts.
Group Activities
Use the in-depth problem-solving investigation ‘Are you well balanced?’ from NRICH as today’s group activity.
Or, use these activities:
-- Find as many ways of making given numbers.
-- Consolidate number bonds to 10 and 20.

Day 2 Teaching
Use the NRICH balances to show equality and use this to rehearse number facts. Write these facts as number sentences, using +, = and also – signs.
Group Activities
-- Play ‘what’s in the box’ exploring different number fact sentences.

### You Will Need

• Coat hanger and 12 pegs (2 colours)
• Bar model pictures for pairs to 6, 7, 8, 9 & 12 (see resources)
• Number balance (or an interactive one)
• Small items for hiding, boxes or bags to hide items in

### Mental/Oral Maths Starters

Day 1
Addition facts for numbers 6 to 10 (pre-requisite skills)

Suggested for Day 2
Pairs to 10 (simmering skills)

### Worksheets

Day 1
Practise number facts.

Day 2
Practise equalities.

### Mastery: Reasoning and Problem-Solving

• Write 4 number sentences to relate these 3 numbers: 13, 19 and 6.
• We know 13 + 7 = 20. So what is 130 + 70?
We know 11 + 9 = 20. So what is 110 + 90?
Repeat this.
• Write three different ways of making 14 by adding two 1-digit numbers.

In-depth Investigation: Are You Well Balanced?
Hang combinations of weights to make the scale balance. Are You Well Balanced? from nrich.maths.org.

### Extra Support

Perfect Pairs
Addition facts for 6, 7, 8, 9 and 10

Patterns Practice
Using addition facts to add single-digit numbers to 2-digit numbers, e.g. using 5 + 3 = 8 to work out 25 + 3 (not crossing 10s)

## Unit 2 Using number facts to add/subtract (suggested as 3 days)

### Planning and Activities

Day 1 Teaching
Use a 1-100 bead bar to demonstrate 5 + 3 is similar to 15 + 3, 25 + 3, 35 + 3, etc. Repeat for 7 + 4, 17 + 4, 27 + 4, 37 + 4, etc. Repeat on landmarked lines.
Group Activities
Use the ‘Puzzling Squares’ in-depth problem-solving investigation below as today’s group activity.
Or, use these activities:
-- Identify mystery numbers by spotting the patterns of adding given 1-digit to 2-digit numbers.
-- Explore adding a given no. to any 2-digit no. that ends in the same digit.

Day 2 Teaching
Use the bead bar to show that 5 – 2 is similar to 15 – 2, 25 – 2, 35 – 2, etc. Repeat for 14 – 7, 24 – 7, 34 – 7. Show on landmarked lines.
Group Activities
-- Play subtraction bingo, taking 1-digit numbers from 2-digit numbers.
-- Card subtraction activity taking 1-digit numbers from 2-digit numbers.

Day 3 Teaching
Demonstrate spotting number facts and doubles to add several numbers.
Group Activities
-- Play tiddlywinks, adding 3 or more numbers.
-- Mystery number bags – adding 3 or more numbers.

### You Will Need

• 0-100 beaded line (see resources)
• 0-100 landmarked line (see resources)
• Additional activity sheets (see resources)
• Number dice (regular, 8-sided and 12 sided)
• Number cards
• 4 bags or pots per group
• 1-digit and 2- digit number cards

### Mental/Oral Maths Starters

Day 1
Complements to multiples of 10 (pre-requisite skills)

Suggested for Day 2
Number facts (simmering skills)

Suggested for Day 3
Doubles 1 to 10 (simmering skills)

### Worksheets

Day 1

Day 2
Subtract 1-digit from a 2-digit-number.

Day 3

### Mastery: Reasoning and Problem-Solving

• Write 8 + 4 = 12 in the middle of a space and circle it. Draw 8 spider legs out from it. Write 8 sentences, each with a 2-digit number, using this central fact.
• Always true, sometimes true or never true?
Adding 7 to a number ending in 4 gives an answer ending in 1.
Taking 6 away from a number gives an answer ending in 2.
Adding 9 to a number always gives a 1s digit which is one less than the number you started with.
• A + B – 12 = 3
What numbers could A and B stand for? Neither is more than 10.

In-depth Investigation: Puzzling Squares
Children use reasoning skills to solve a number puzzle. They use numbers 0 to 7 to make a total of 10 on each side of a square.

### Extra Support

This unit has no separate Extra Support activities.

## Unit 3 Add/subtract: efficient mental strategies (suggested as 3 days)

### Planning and Activities

Day 1 Teaching
Introduce maths Frog. Show how Frog hops up along a number line to help us count up to find a difference, e.g. 70 – 56, Frog hops from 56 to 60, and then to 70. Stress that Frog always hops first to the next 10.
Group Activities
-- Frog pairs game subtracting two 2-digit numbers.

Day 2 Teaching
Rehearse the list of rules for how Maths Frog counts up. Use these to help Maths Frog to find greater differences, e.g. 92 – 48.
Group Activities
Use the ‘Twisted Subtraction’ in-depth problem-solving investigation below as today’s group activity.
Or, use these activities:
-- Jumping frogs and dog lengths: subtract by counting up.

Day 3 Teaching
Explain that Maths Frog can help us find change from £1. Show how Frog hops from 67p to 70p to £1 to find change from 67p.
Group Activities
-- Pick a badge activity - finding change from £1.
-- Use bar models to create subtractions which require Frog to help us find the change from £1.

### You Will Need

• Maths Frog toy
• 0-100 landmarked line
• 0 to £1 (see resources)
• 0-100 beaded lines (see resources)
• Additional activity sheets (see resources)
• Toy dogs (or similar) of different sizes
• Money
• Items to sell

### Mental/Oral Maths Starters

Day 1
Complements to multiples of 10, e.g., 57 + □ = 60 (pre-requisite skills)

Day 2
Subtraction number bonds to 10 (pre-requisite skills)

Suggested for Day 3
Use place value to add and subtract (simmering skills)

### Worksheets

Day 1
Subtract by counting up.

Day 2
Subtract two 2-digit numbers.

Day 3
Find change from £1.

### Mastery: Reasoning and Problem-Solving

• Write two 2-digit numbers with a difference of 8.
• Write 3 different subtractions where Frog does 2 hops and the first is 4.
8 ☐ – 4 8 = 3 4
☐ 5 – 2 7 = 6 ☐
• Write a subtraction where the 10s digit in the smaller number is 2 less than the 10s digit in the bigger number and the answer is 16.

In-depth Investigation: Twisted Subtractions
Children subtract a number which is the reverse of another, e.g. 62 - 26.

### Extra Support

Tiptoe to 10
How many to the next 10, e.g. 36 + □ = 40?

## Unit 4 Partitioning to add (suggested as 2 days)

### Planning and Activities

Day 1 Teaching
Demonstrate how we can add 2-digit numbers by partitioning each one into 10s and 1s. So 65 + 24 = 60 + 20 + 5 + 4. Use place value equipment to demonstrate this.
Group Activities
Use the in-depth problem-solving investigation ‘Diagonal Sums’ from NRICH as today’s group activity.
Or, use these activities:
-- Spinners: adding to make less than and more than 100.

Day 2 Teaching
Use place value equipment to add pairs of 2-digit numbers by partitioning each one into 10s and 1s, and noticing that if we wind up with more than ten 10s, we have 100.
Group Activities
-- Pocket money promotion activity adding to make more than & less than 100 in pounds and pence.

### You Will Need

• Place value cards
• ITP: Place Value
• Spinners (see resources)
• Cards (to write additions on)
• Pocket money badges (see resources)

### Mental/Oral Maths Starters

Day 1
Add pairs of multiples of 10 (pre-requisite skills)

Suggested for Day 2
Number bonds (simmering skills)

Day 1

Day 2

### Mastery: Reasoning and Problem-Solving

• Write 2 numbers which total 91 where one has a 1s digit of 6.
• Write the missing digits:
7 ☐ + 4 8 = ☐ 2 4
☐ 5 + 8 7 = 1 4 ☐
• How many pairs of numbers between 20 and 30 can you find that total 51?

In-depth Investigation: Diagonal Sums
In a square of numbers on the 100-grid, explore the sum of the pairs of numbers that are diagonally opposite each other. Diagonal Sums from nrich.maths.org.

### Extra Support

Splitting Sums
Adding 10s numbers; beginning to use partitioning to add pairs of 2-digit numbers