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Addition and Subtraction
Objectives
To add a single-digit number to a 2-digit number, bridging 10.
Resources
Abacus Workbook 1 | 📄 0-100 beaded line | 📄 0-100 landmarked line | 100 Beadstring | Assignment 5
Vocabulary
add | bridge 10
Today's Lesson
Assignment
This lesson works towards Assignment 5. Please access the assignment for details about what you will need to submit to your student's Wolsey Hall tutor.
What to Get Ready
Print off Assignment 5.
Introduction
Before you start the lesson, watch this Recap Video with your student.
Main Activity
Show 28 beads on the 100 Bead String.
Say: ‘We’re going to add 5 beads.’
Slowly slide a group of 5 beads along to join them.
Ask: ‘What do you notice?’ (That 2 of the 5 beads completed a whole 10 and there are 3 more.)
Ask: ‘What is the next multiple of 10 after 28? 30.
Can you point to the beads we added to 28 to make 30?
How many did we add? 2.
What would 30 add 3 be?’
Explain that we call this strategy ‘Target the 10s’ or ‘T10’ for short, as we’re trying to land on a multiple of 10 to help us add the single-digit number.
Show recording it like this for this:
This method of recording shows how the single-digit number has been split to help make adding easier.
Remind your student how important it is to know their number pairs to 10. This helps them to use the T10 strategy. They may like to use the 📄 0-100 beaded line to help them jump to the nearest multiple of 10.
Repeat with:
38 + 5 (38 + 2 + 3)
25 + 7 (25 + 5 + 2)
46 + 7 (46 + 4 + 3)
57 + 7 (57 + 3 + 4)
Now try these:
45 + 8
67 + 5
38 + 7
Ask them to record their working on Assignment 5**.**
Note: The completed assignment should be submitted to your student’s tutor at the end of Step 15 Lesson 5.
Extra Challenge
Ask your student to use the 📄 0-100 landmarked line during the task, which will make them think harder!
Then, write: 55 + 7 = 62 in the middle of a page. Draw at least 4 lines out from it, rather like a spider! At the end of each line, ask your student to write a calculation that you can do easily because you have worked out the sum in the centre.
For example:
- 15 + 7
- 17 + 5
- 35 + 7
- 37 + 5
- 32 – 7
Workbook
To help your student recap upon previous learning from this course, please ask them to complete the activities on page 19 of Abacus Workbook 1.