New
New
Year 1

Use knowledge of subtraction facts within 10 to subtract within 20

I can use knowledge of subtraction facts within 10 to subtract within 20

New
New
Year 1

Use knowledge of subtraction facts within 10 to subtract within 20

I can use knowledge of subtraction facts within 10 to subtract within 20

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Lesson details

Key learning points

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

Common misconception

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

Make comparisons between subtraction within 10 and within 20, looking for patterns. Make sure children notice that the ones digit stays the same when we subtract numbers with the same ones digits such as 5 - 2 and 15 - 2.

Keywords

• Subtraction - To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.

• Minus - A synonym for subtract, represented by the symbol -

• Difference - The result of subtracting one number from another. How much one number differs from another.

Use number lines to show subtraction within 10 and within 20, drawing out the similarities. Make sure children notice that the ones digit stays the same when we subtract 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 could the two missing parts be?
1 and 7
3 and 3
Q3.
Which of these symbols means minus?
+
=
Q4.
Andeep has 5 biscuits and eats 3 of them. How many does he have left? Which equation represents this?
5 + 3 =
Correct answer: 5 − 3 =
3 − 5 =
Q5.
Izzy has 12 hair clips. 10 are pink and the rest are blue. How many are blue? hair clips
Q6.
Sofia has 17 hair clips. She loses 7 of them. How many hair clips does she have now? hair clips

Exit quiz

6 Questions

Q1.
Which of these part-part-whole models match the story? First Izzy had 19 strawberries and then she ate 5 of them. How many strawberries does she have left?
Correct Answer: An image in a quiz
Q2.
Which equation below helps you to find the answer to 13 − 2 = ___?
13 − 3 = 10
Correct answer: 3 − 2 = 1
13 + 2 = 15
Q3.
Complete the sentence: 7 minus 2 is equal to 5, so 17 minus 2 is equal to