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Addition and Subtraction
Objectives
To add near multiples of 10 by adjusting.
Resources
Abacus Workbook 1 | 📄 Nearly number board | Sticky notes | Counters | 📄 100 square
Vocabulary
near multiples | adjust
Today's Lesson
What to Get Ready
Print and cut the 📄 Nearly number boards in half so that there are two separate boards, ready for the Main Activity.
Introduction
Before you start the lesson, watch this Recap Video with your student.
To progress from working with multiples of 10, show the strategy for adding and subtracting 11, 21, 31, and so on, by asking your student how they might use the 📄 100 square to help them do this.
Draw out that, when, for example, adding 11, a good strategy is to add 10 by jumping down one row, then to add 1 by jumping across one.
Ask: ‘So how would we subtract 11?’ (Jump up one, then jump left one.).
Ask: ‘What about adding and subtracting 21 or 31?’
Discuss this and give your student some time to explore adding and subtracting 11 initially, then to progress to 21, 31, and so on.
Main Activity
Using the 📄 100 square and the 📄 Nearly number boards, take it in turns with your student to:
- Choose a number from the grid, for example, 34.
- Choose a nearly number from the coloured circles, for example, 19.
- Write an addition, for example, 34 + 19 =
- Using the 📄 100 square to help, add a multiple of 10 and adjust, write the total for the addition and then write it on a sticky note, for example, 53
Check each other’s addition. If correct, cover the chosen number on the grid (34 in this case), with a counter.
Continue to take it in turns until you have covered all the numbers on your boards.
Workbook
To help your student consolidate their learning from today, please ask them to complete the activities on page 43 of Abacus Workbook 1.