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. 'Teaching for Understanding' provides whole-class teaching and fully differentiated adult-led group activities. ‘Problem-solving and Reasoning’ develops these skills, and includes questions to enable you to assess mastery. Practice sheets ensure procedural fluency. Extra support activities enable targeted work with children who are well below ARE.

‘UNIT PLAN’ gives you a text version of all parts of the unit to use in your school planning documentation. ‘DOWNLOAD ALL FILES’ gives you that unit plan plus all of associated documents.

Unit 1 Using place value to add/subtract (suggested as 5 days)

Objectives

Using place value to add/subtract
Unit 5: ID# 3209

National Curriculum
Add/Sub (iv) (i)

Hamilton Objectives
9. Add and subtract multiples of 1, 10 and 100 to/from 3-digit numbers.
3. Understand place value in 3-digit numbers.
5. Solve number problems & practical problems involving place value.

Additional
Add and subtract near multiples of 1, 10 and 100 to/from 3-digit numbers.

Teaching and Group Activities for Understanding

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 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)

Procedural Fluency

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. Write 3 different subtractions to get a final answer of 500. How would these change if you wanted a final answer of 499?
  • Add 80 to 263 then subtract 1. How much bigger is your answer than 263?
  • 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.

Extra Support

Jolly Jumping
Adding 9 to 2-digit numbers

Super Simple Subtractions
Subtracting 9 from 2-digit numbers

Unit 2 Mental calculation – complements to 100 (suggested as 2 days)

Objectives

Mental calculation – complements to 100
Unit 6: ID# 3221

National Curriculum
Add/Sub (i) (iii)

Hamilton Objectives
8. Mentally add or subtract any pair of 2 digit numbers, including pairs to 100.
7. Know securely number pairs for all the numbers up to and including 20.
12. Subtract larger numbers with confidence, using 'Frog' for counting up, e.g. either side of 100.

Additional
Know pairs of multiples of 5 that total 100.

Teaching and Group Activities for Understanding

Day 1 Teaching
Use the bead bar to demonstrate the pairs of multiples of 5 that total 100, e.g. 10 and 90, 15 and 85, etc. Record and rehearse these aloud.
Group Activities
-- Pairs to 100 bar game: finding pairs of multiples of 5 that total 100.
-- Complements to 100: pairs of multiples of 5 that total 100 and corresponding subtractions.
-- Thumbs up, thumbs down: identifying pairs of multiples of 5 that total 100.

Day 2 Teaching
Use the bead bar to demonstrate that we can count up from 67 to 70 and from 70 to 100. So 67 + 33 = 100. Hide the complement of 56 under a cloth on the bead bar and encourage children to work it out by performing the hops in their heads.
Group Activities
Use the ‘Closest to 100’ in-depth problem-solving investigation below as today’s group activity.
Or, use these activities:
-- Split the bead bar: complements to 100
-- Four in a row: complements to 100
-- Subtraction challenge: finding additions that help solve subtractions

You Will Need

  • 100 bead bar & bead string
  • Cloth & rectangles of coloured card
  • 0-100 landmarked line (see resources)
  • 0-100 beaded line (see resources)
  • Cubes
  • Additional activity sheets (see resources)

Mastery: Reasoning and Problem-Solving

  • Write 4 sentences to link the numbers 45, 100 and 55.
  • What mistake has Fred made in each of his sums?
    1. 63 + 47 = 100
    2. 26 + 84 = 100
    3. 41 + 69 = 100
    Correct each one for him.
  • Write all additions of this form: __ + __ = 100 where 1 of the numbers has 2 digits the same.


In-depth Investigation: Closest to 100
Following simple rules children find ways to make 100 based on four dice throws. They practise adding four numbers with a total around 100 and use this to find a solution.

Extra Support

Tens Jigsaws
Finding, then knowing by heart pairs of numbers with a total of 10

Unit 3 Mental subtraction – counting up (suggested as 3 days)

Objectives

Mental subtraction – counting up
Unit 7: ID# 3229

National Curriculum
Add/Sub (i) (iv)

Hamilton Objectives
12. Find a difference between a 3-digit and a 2-digit number by counting up.
10. Recognise that there are 2 ways of completing subtractions, either by counting up or by counting back.
13. Estimate answers and use addition to check subtraction, understanding that addition and subtraction are inverse operations.


Teaching and Group Activities for Understanding

Day 1 Teaching
Remind children of Maths Frog. Demonstrate how we can count up along an empty number line using Frog to work out the difference between 87 and 102. Model several subtractions.
Group Activities
-- Frog jump cards: subtract 2-digit numbers from 3-digit numbers.
-- Investigation: subtract 2-digit numbers from 3-digit numbers to find answers of 15.

Day 2 Teaching
Demonstrate counting up using Frog hopping along a number line to show how we calculate 113 – 78. Stress how we add the hops to find the answer.
Group Activities
-- Cricket scores: finding the difference between 2 numbers.

Day 3 Teaching
Use Frog and the empty number line to perform subtractions (112 – 76) and make deliberate errors which children have to correct.
Group Activities
Use the in-depth problem-solving investigation ‘Dicey Operations’ from NRICH as today’s group activity. Or, use these activities:
-- Making subtractions: 2-digit from 3-digit numbers with answers less than 40.
-- Change from £1: subtracting 2-digit numbers from 100.
-- Frog jumps or counting back: choosing the right approach.

You Will Need

  • Maths Frog toy
  • Red and blue Frog jump cards (see resources)
  • Table of jumps children made (see resources)
  • Additional activity sheets (see resources)
  • Money

Procedural Fluency

Day 1
Subtract 2-digit numbers from 3-digit numbers.

Day 2
Subtract by counting up: answers less than 30.

Day 3
Subtract by counting up: answers less than 40.

Mastery: Reasoning and Problem-Solving

  • Write 3 pairs of numbers with a difference of 17. 1 of the numbers must be more than 100, 1 must be less than 100.
    76 + __ = 112
    106 – 68 = ___
    11 ☐ – 8 7 = 2 5
  • What must be added to 88 to give 114?
    What must be added to 77 to give 115?
  • What change will I get if I buy two pairs of trainers for £33 each and pay with two £50 notes?
  • Tim has saved £112. He spends £87 on a new game. How much does he have left?


In-depth Investigation: Dicey Operations
Adapt Game 2 and use counting up to find a 3-digit-2-digit difference closest to 500. Dicey Operations from nrich.maths.org.

Extra Support

A Hop and a Jump
Finding how many are needed to make the next 10, and the next 10 after that, e.g. 37 + ? = 40, and 37 + ? = 50