Mathematics
Intermediate
50 mins
Teacher/Student led
+65 XP
Teacher-led from the board. Pupils do not need a device, but can follow on one.
What you need:
IWB/Projector/Large Screen

Multiplying a 2-digit Number by 1 Digit: Split the Rectangle Into Boxes

Learn to multiply two-digit numbers by one digit using partition and the split-rectangle area model. Split the number into tens and units, multiply each part separately, then add the partial products together.

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    Area model
    Word problem

    1 - Getting Started ~4 mins

    A shop wall of four identical shelves, each packed with the same row of tins of beans.A shop stacks its shelves in rows. One shelf holds 23 tins of beans, and there are 4 shelves the very same. Roughly how many tins is that on the wall altogether? Hands up: is it closer to 80, or closer to 100?

    We could count every tin one by one, but that would take an age. Today we will find a quick, tidy way to work out 23 × 4 and sums like it.

    2 - Watch and Notice ~8 mins

    The interactive draws each multiplication as a rectangle that splits into two boxes. Watch where the two-digit number breaks into tens and units, and how each box gets multiplied on its own before we add them.

    3 - Try It Together ~9 mins

    Now we build 34 × 6 together on the split rectangle. The 34 splits into a tens box and a units box, and we add the two partial products for the answer. Watch the board, predict the big box first, then we check it together.

    After that, I will work two more on the board with you: 28 × 5 and 56 × 4. Watch the units box in 28 × 5 — it gets big, so the adding needs care.

    Split the rectangle into boxes

    4 - Build the Boxes in Your Copy ~3 mins

    COPYBOOK MOMENT

    Illustration for Build the Boxes in Your CopyIn your maths copy, draw a rectangle split into two boxes for 34 × 6, and another for 46 × 5, just like the ones on the board. Fill in each partial product, then add the two boxes to find the answer for each one.

    • 34 × 6
    • 46 × 5

    Remember to split the two-digit number into tens and units before you fill the boxes.

    5 - Class Challenge ~8 mins

    Today we solve these shop-and-sport problems together: first 21 stickers on each of 4 pages, then 34 cones costing €5 each, then 47 euro raised by each of 6 pupils, and finally 58 metres run in each of 7 laps. Read each story, spot the words that tell you to multiply, then split the rectangle into boxes to find the answer. The later ones have a units box that carries when you add.

    Split-the-rectangle shop and sport problems

    Pupil practice
    Module 2 · The Four Operations: Mental and Written Number
    Lesson 24 · Multiplying a 2-digit Number by 1 Digit: Split the Rectangle Into Boxes
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