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Calculations

Objectives

To write place value additions and subtractions.

Resources

Abacus Workbook 3 | Place value arrow cards | Calculator | Interactive Place Value (Mathsframe) | 📄 3-digit numbers

Vocabulary

Today's Lesson

What to Get Ready

Addition

Give your student the cut-out Place value arrow cards used in Lesson 4.

Ask:

What is 100 add 23? Show me.

Ask them to use the cards to make 23 then show you.

Then ask them to show you 123.

Ask:

What have you done?

Discuss the addition you could write and record: 100 + 20 + 3 = 123 and 100 + 23 = 123.

Ask:

Now show me 120. How many cards did you need?
Now show me 123. What have you done?
What addition could we write?

Record: 120 + 3 = 123.

Ask:

Now show me 103. What do we add to get back to 123?
What addition could we write?

Record: 103 + 20 = 123.

What a lot of additions we can write when we understand place value!

Make 345, then write as many additions as you can that use these cards.

Subtraction

Make and display the number 342.

Ask:

How could we ‘zap’ the 4 digit to leave a zero in its place (302)?
Would there be a zero if we subtracted 4? Why not?

Say:

Make the number with your cards and try out some ideas. So, what should we subtract?

Record: 342 – 40 = 302. The 4 is in the 10s place, so to ‘zap’ the 4, we need to subtract 4 tens, or 40.

Ask:

How could we get the 4 digit back again?

Agree that you must add 40.

Record: 302 + 40 = 342.

Repeat to ‘zap’ the 2, recording: 342 – 2 = 340.

Watch this video which uses the interactive place value cards on Mathsframe to help demonstrate these calculations with 3-digit numbers.

Main Activity

Type the number 356 into a calculator.

Ask:

How you could we ‘zap’ the 3 digit?
Would there be a zero if we subtracted 3? Why not?

Ask your student to try out other ideas. What should we subtract?

They should then subtract 300 on their calculator: 356 – 300 = ____

Ask them how they could get the 3 digit back again. Agree that they must add 300.

Repeat to ‘zap’ the 6.

Ask:

What could we do?
What digit would be in the ones place then?

Subtract 6, then ask:

How can we change the 0 back to 6?

Repeat ‘zapping’ and returning 100s, 10s or 1s digits for other numbers, for example, 523, 741, 906.

Extra Challenge

Complete the **📄 3-digit numbers**sheets, filling in the missing numbers in 3-digit place value additions and subtractions.

Workbook

To help your student build upon their learning from today, please ask them to complete the activities on page 45 of Abacus Workbook 3.

Quiz

PRACTISE - Step 35 Quiz

*All quizzes on this course are optional, they do not count towards your student’s grade. If you decide to do them, they are a chance to explore your student's understanding of different topics.

If your student finds reading tricky, you can read them the questions.

If your student is unsure of an answer, talk with them about their ideas. You can also look back at previous lessons together.*

Citations

[1] mathsframe.co.uk