Short Blocks

# Maths Year 3 Autumn Addition and Subtraction (B)

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

## Using place value to add/subtract(suggested as 5 days)

### Planning and Activities

Day 1 Teaching
Display a place value grid and write 3-digit numbers on it. Show which digit changes if you add multiples of 10. Repeat to show which digit changes if you add multiples of 100. Repeat for 1s.
Group Activities
-- Spinners: adding 1s, 10s and 100s to 3-digit numbers.
-- Making Money: adding multiples of 1s and 10s.

Day 2 Teaching
Use a place value grid to show which digit changes if you subtract multiples of 10. Repeat for multiples of 100 or 1.
Group Activities
-- Cake cards: subtracting 1s, 10s and 100s from 3-digit numbers.

Day 3 Teaching
Demonstrate how to add and subtract near multiples of 10 to/from 2-digit numbers using a number line, and also a 1-100 number grid.
Group Activities
Use the ‘Magic 147’ in-depth problem-solving investigation below as today’s group activity.
Or, use these activities:
-- Near Multiples Game: adding and subtracting multiples of 10 and related near multiples.
-- Alien Attack: adding multiples of 10 and related near multiples

Day 4 Teaching
Use an empty number line to model the hops involved in adding a near multiple of 10 to a 3-digit number: 225 + 29 is 225 hop 30 along and then back 1, etc.
Group Activities
-- Hexagon Multiples Game: adding multiples of 10 and related near multiples.

Day 5 Teaching
Use an empty number line to model the hops involved in subtracting a near multiple of 10 from a 3-digit number. Demonstrate how we adjust the hops to subtract 51 or 49 rather than 50.
Group Activities
-- Hexagon Multiples Game: subtracting multiples of 10 and related near multiples.

### You Will Need

• Place value grid (see resources).
• Spinners (see resources).
• 10ps & 1ps.
• Cake cards (see resources).
• 100 square.
• Near Multiples Game Board (see resources).
• Coloured counters.
• Number lines or 100 squares.
• Alien Attack online game.
• Hexagon Multiples Addition Game board and cards (see resources).
• Hexagon Multiples Subtraction Game board and cards (see resources).

### Mental/Oral Maths Starters

Day 1
Add/subtract multiples of 10 to or from any 2-digit number (pre-requisite skills)

Suggested for Day 2
Pairs to 20, and related subtractions (simmering skills)

Suggested for Day 3
Add any pair of single-digit numbers (simmering skills)

Day 4
Count on and back in 10s from a 3-digit number (pre-requisite skills)

Suggested for Day 5
Count in 2s from any 3-digit number (simmering skills)

### Worksheets

Day 1
Add multiples of 1s, 10s and 100s to 3-digit numbers.

Day 2
Subtract multiples of 1s, 10s and 100s from 3-digit numbers.

Day 3
Find the missing number: near multiples.

Day 4
Add multiples and near multiples of 1s, 10s and 100s to 3-digit numbers.

Day 5
Subtract multiples and near multiples of 1s, 10s and 100s to 3-digit numbers.

### Mastery: Reasoning and Problem-Solving

• Start with 789. What three numbers could you subtract to get a final answer of 500? How would these calculations change if you wanted a final answer of 499?
• Use number cards 9, 1, 5 and 7. How many additions of near multiples can you create?
• Mystery number
What ONE number makes this sentence true?
76 – ? = 18 + ?
• How many times will you add 19 to 24 to reach 100? What number will you start with if you add 18 repeatedly and reach 100 exactly?

In-depth Investigation: Magic 147
Children arrange the ‘nearly numbers’ in a square so that each row and column adds to Magic 147.

Jolly Jumping