Bonds to multiples of 100

Objectives

To work out strategies for finding missing numbers.

To make a connection between addition and subtraction within mathematical sentences.

Resources

Abacus 4 Textbook 1 | Squared paper | Timestables (TopMarks) | Frog Method (YouTube) | Number bonds to 100 (YouTube)

Today's Lesson

Main Activity

As a mental warm up, after practising times tables, (use Timestables (TopMarks) if required), ask your student some random questions on number bonds to 10 and 100.

For example:

8 + ? = 10 ? + 3 =10 10 – 6 = ?

42 + ? = 100 ? + 67 = 100 100 - ? = 26

If needed, watch Number bonds to 100 (YouTube) to recap when numbers are not multiples of 10.

Discuss one of the examples from the video with your student (E.g. 19 + ? = 100) and then ask them to remind you of the 3 simple steps.

Step 1: Count to the nearest 10.
19 + 1 = 20

Step 2: Count in tens to 100.
20 + 80 = 100

Step 3: Add the jumps together
1 + 80 = 81 so we know that our missing number is 81
19 + 81 = 100

Repeat with other examples if needed.

Turn to page 5 in Abacus 4 Textbook 1. You will notice that these questions relate to multiples of 100.

Watch Frog Method (YouTube) to see how your student can easily calculate these bonds to 200.

Use this knowledge to help with number bonds to different multiples of 100 and continue to use the simple steps to find the missing numbers.

Step 1: Count to the next 10
Step 2: Count in tens to the next 100
Step 3: Add the jumps.

Before your student starts the calculations, discuss Q2. Ask them how this is different to what they have done before. (An additional step will be needed.)

Step 1: Count from 78 to 80 (A jump of 2)
Step 2: Count from 80 to 100.(A jump of 20)
Step 3 (an additional step): Count in 100s to 400 (A jump of 300)
Step 4: Add the jumps. (2+20+300)

Ask your student to complete Q1-16.

Look at Q17-19 together.

Following on from the real-life problems in the previous lesson, remind your student to find key vocabulary to help work out which calculation will be needed to solve the problems. Your student should write the calculation, show all working out and then make sure they include the unit of measure (e.g. £ or m) with their answer.

Further to the previous lesson, ask your student to apply the strategies of choice to copy and complete the calculations on the remainder of the page.

Citations

[1] youtu.be [2] www.youtube.com [3] www.youtube.com [4] www.youtube.com [5] www.topmarks.co.uk