New
New
Year 3

Subtract a pair of 2-digit numbers by finding the difference

I can subtract a pair of 2-digit numbers by finding the difference.

New
New
Year 3

Subtract a pair of 2-digit numbers by finding the difference

I can subtract a pair of 2-digit numbers by finding the difference.

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Lesson details

Key learning points

  1. When the minuend and subtrahend are close in value, finding the difference can be an efficient strategy for subtraction
  2. Finding the difference means we count on from the subtrahend or count back from the minuend
  3. A number line or a bar model can represent finding the difference

Keywords

  • Minuend - The minuend is the number being subtracted from.

  • Subtrahend - A subtrahend is a number subtracted from another.

  • Difference - The difference is the result after subtracting one number from another.

Common misconception

Pupils will often try to use a written method/algorithm which they know gives an accurate answer but don't understand why it works.

Encourage the pupils to be brave and remind them that this is about mental subtraction so, with practice, will be quicker than any written methods.

This strategy is shown with number lines and jottings but the end goal is for the children be able to do it mentally so try to reduce such supports as quickly as possible.
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).

Lesson video

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6 Questions

Q1.
What number is represented by these place value counters?
An image in a quiz
10
Correct answer: 343
433
Q2.
What number is represented by the base ten blocks?
An image in a quiz
442
10
Correct answer: 244
424
Q3.
Choose the correct symbol to go between the expressions. 7 + 5 ___ 3 + 4
Correct answer: >
<
=
Q4.
Choose the correct symbol to go between the expressions. 20 − 3 ___ 12 + 10
>
Correct answer: <
=
Q5.
Choose the correct symbol to go between these expressions. 34 − 10 ___ 14 + 10
>
<
Correct answer: =
Q6.
Using your understanding of place value, order these numbers from smallest to greatest.
1 - 10
2 - 30
3 - 31
4 - 103
5 - 130
6 - 301
7 - 310

6 Questions

Q1.
Match the numbers with words for the equation 8 − 6 = 2
Correct Answer:8,Minuend

Minuend

Correct Answer:6,Subtrahend

Subtrahend

Correct Answer:2,Difference

Difference

Q2.
Which of these bar models represents finding the difference?
Correct Answer: An image in a quiz
An image in a quiz
An image in a quiz
An image in a quiz
Q3.
Which of these contexts does not involve finding the difference?
How many more sweets have I eaten?
Correct answer: How many sweets do we have altogether?
How many more sweets do I have compared to you?
Q4.
Which of these subtraction expressions can be more efficiently solved by finding the difference?
81 − 43
Correct answer: 81 − 76
45 − 16
Correct answer: 98 − 89
Correct answer: 73 − 66
Q5.
67 − 58 =
Correct Answer: 9, nine
Q6.
= 96 − 89
Correct Answer: 7, seven