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Addition and Subtraction
Objectives
To add 2-digit numbers by adding multiples of 10 then ones.
Resources
Abacus Workbook 1 | 📄 Adding 2-digit numbers | 📄 0-100 landmarked line
Vocabulary
addition | tens | ones
Today's Lesson
Introduction
Show your student the 📄 0-100 landmarked line and ask, ‘What is 45 add 20? Do we need to count on in ones?’
Ask your student to mark 45 on the landmarked line, and to draw two jumps of 10, labelling them ‘+10’, and labelling 65.
Ask: ‘How could we work out 45 add 24?’
Encourage them to come up with some ideas.
Explain that we can add 24 by adding on 20 as before, and then adding on 4.
Ask: ‘What number fact can we use to help?’
Explain that we know 5 add 4 is 9, so 65 add 4 is 69. So, we still do not need to count on in ones! Draw the hop of +4 and label 69 under the line.
Ask them to talk with you about how we might work out 65 add 24.
Write this calculation (65 + 24) on the landmarked line and tell them that they do not need to label 75, but just to count on 20 in their heads, and label where they land afterwards (85); then hop another 4 to 89.
Repeat for 52 + 30, 52 + 33, 72 + 33 and 46 + 32, asking them to help you to draw the jumps and hops on the landmarked line.
This video will demonstrate using the landmarked line to help add together 2-digit numbers in this way.
Main Activity
Ask your student to complete the 📄 Adding 2-digit numbers tasks.
Workbook
To help your student consolidate their learning from today, please ask them to complete the activities on page 52 of Abacus Workbook 1.