New
New
Year 1

# Use knowledge of addition facts within 10 to add within 20

I can use knowledge of addition facts within 10 to add within 20

New
New
Year 1

# Use knowledge of addition facts within 10 to add within 20

I can use knowledge of addition facts within 10 to add within 20

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## Lesson details

### Key learning points

1. Addition facts within ten can be applied to addition within 20, e.g. if 3 + 2 is equal to 5 then 13 + 2 is equal to 15
2. A number line can be used to show the link between addition of one-digit numbers and teen numbers

### Common misconception

Children may rely on counting strategies instead of using known facts to add larger numbers.

Make comparisons between addition within 10 and within 20, looking for patterns. Make sure children notice that the ones digit stays the same when we add numbers with the same ones digits such as 3 + 2 and 13 + 2.

### Keywords

• Addition - Bringing two or more numbers or things together to make a new total.

• Add - Bringing two or more numbers or things together to make a new total.

• Plus - A synonym for add, represented by the symbol +

Use number lines to show addition within 10 and within 20, drawing out the similarities. Make sure children notice that the ones digit stays the same when we add numbers with the same ones digits.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
What is the missing part?
Q2.
What is the sum of the parts in this picture?
Q3.
Which equation represents this part-part-whole model?
Correct answer: 9 = 1 + 8
Correct answer: 8 + 1 = 9
8 = 1 + 9
9 + 1 = 8
Q4.
I have 7 pencils altogether. 3 are red and 4 are yellow. Which equations would represent this?
3 + 7 = 4
Correct answer: 7 = 3 + 4
3 = 7 + 4
Q5.
What does the 2 represent in this equation? 2 + 8 = 10
The whole group.
The counters we can see.
Q6.
Use the number patterns in the equations to find the missing addend in the last equation. 4 + 0 = 4 3 + 1 = 4 2 + 2 = 4 1 + = 4

## Exit quiz

### 6 Questions

Q1.
Which of these part-part-whole models match the story? First Izzy ate 11 strawberries and then she ate 5 more. How many strawberries has she eaten?
Correct Answer: An image in a quiz
Q2.
Which equation below helps you to find the answer to 13 + 6 = ___?
10 + 6 = 16
Correct answer: 3 + 6 = 9
10 + 3 = 13
Q3.
Complete the sentence: 1 plus 7 is equal to 8, so 11 plus 7 is equal to