Short Blocks

Maths Year 3 Spring Addition & Subtraction (A)

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

Mental addition of 2-digit numbers (suggested as 2 days)

Planning and Activities

Day 1 Teaching
Discuss what strategies we can bring to adding two 2-digit numbers. We start with the larger number. We look for number bonds to help us. We may partition or add multiples of 10 and near multiples of 10.
Group Activities
Use the in-depth problem-solving investigation ‘Dicey addition’ from NRICH as today’s group activity.
-- Use spinners to generate 2-digit numbers to add. Children discuss which strategy to use each time.

Day 2
Explain that today we will add three 2-digit numbers.
Show 3 snakes each with their length labelled: 42cm, 18cm, 25cm. Children discuss in pairs and then share how they would find the total length.
Group Activities
-- Choose 2 or three 2-digit numbers to add, ring answer on a grid. Try to get 3 in a line.

You Will Need

  • Large 1-100 grid
  • Plastic/card spider and fly
  • ‘2-digit number spinners’ sheet 1 (see resources, enlarge to A3)
  • A paper clip, 10s and 1s place value cards
  • ‘2-digit number spinners’ sheet 2 (see resources)
  • 1 to 100 number grid (see resources)
  • Six snakes/ribbons/caterpillars each with length labelled: 43cm, 18cm, 25cm, 57cm, 48cm, 23cm
  • Red and blue pencils/pens
  • Additional activity sheets (see resources)

Mental/Oral Maths Starters

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

Day 2
Add 3 or 4 numbers (pre-requisite skills)

Worksheets

Day 1
Use Spider and Fly to add pairs of number which don’t cross 10s.
Add pairs of amounts of money. Find as many pairs with a total of less than £1 as they can.

Day 2
Add pairs then trios of 2-digit numbers, and then answer word problems.

Mastery: Reasoning and Problem-Solving

  • Use a different strategy for each of these additions:
    45 + 29
    45 + 34
    65 + 35
    78 + 28
  • Complete the bar model diagrams:
    Diagram 1
?
3637

Diagram 2

?
5739

Diagram 3

?
4824

In-depth Investigations: Dicey Addition
Use dice to generate two 2-digit numbers. Find the total. Whoever has the total closest to 100 wins. Dicey Addition from nrich.maths.org.

Extra Support

Do the Splits
Adding pairs of 2-digit numbers using partitioning (1s < 10, 10s < 100)