Use knowledge of addition facts within 10 to add within 20 | Maths

Starter quiz

What is the missing part?
- '1' ✓
What is the sum of the parts in this picture?
- '10' ✓
Which equation represents this part-part-whole model?
- 9 = 1 + 8 ✓
- 8 + 1 = 9 ✓
- 8 = 1 + 9
- 9 + 1 = 8
I have 7 pencils altogether. 3 are red and 4 are yellow. Which equations would represent this?
- 3 + 7 = 4
- 7 = 3 + 4 ✓
- 3 = 7 + 4
What does the 2 represent in this equation? 2 + 8 = 10
- The hidden counters. ✓
- The whole group.
- The counters we can see.
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
- '3' ✓

Exit quiz

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?
Which equation below helps you to find the answer to 13 + 6 = ___?
- 10 + 6 = 16
- 3 + 6 = 9 ✓
- 10 + 3 = 13
Complete the sentence: 1 plus 7 is equal to 8, so 11 plus 7 is equal to ______
- '18' ✓
Complete the sentence: 6 plus 3 is equal to 9, so 16 plus 3 is equal to ______
- '19' ✓
First, Izzy collected 12 stones and then she found 6 more. How many stones does she have now? ______ stones
- '18' ✓
First, Andeep had 11 stickers and then Izzy gave him 5 more. How many stickers does Andeep have now? ______ stickers
- 16
- sixteen

Worksheet

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Presentation

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Lesson Details

Key learning points

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
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 +