New
New
Year 3

Identify knowns and unknowns in subtraction equations

I can identify knowns and unknowns in subtraction equations.

New
New
Year 3

Identify knowns and unknowns in subtraction equations

I can identify knowns and unknowns in subtraction equations.

Lesson details

Key learning points

  1. Equations can be represented using part-part-whole or bar models.
  2. If the minuend is missing, you add the subtrahend and difference.
  3. To find a missing part in a subtraction equation, subtract the other part from the whole.

Common misconception

Pupils may rely on the same strategies to solve all problems and may find it hard to remember when to add to find the missing part and when to subtract.

Emphasise the use of bar models, especially for pupils who are struggling. This will help them identify whether a part is missing or if the whole is missing, and whether they should add the parts or subtract a part from the whole to get the answer.

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.

Bar models and number lines may be useful for this session. The numbers involved should be very familiar to pupils, but they may find the concept of subtraction calculations with missing parts challenging, especially deciding when they should use addition or subtraction to find the answer.
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).

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6 Questions

Q1.
Which number represents the subtrahend in this equation? 31 − 10 = 21
31
21
Correct answer: 10
Q2.
What is the difference between 19 and 21?
Correct Answer: 2, two
Q3.
What is 100 − 30 =
Correct Answer: 70, seventy
Q4.
What is 200 − 50 =
Correct Answer: 150, one hundred and fifty
Q5.
Calculate the missing number is this equation: 40 + ___ = 220
160
170
Correct answer: 180
200
Q6.
Which pairs of numbers have a sum of 600?
100 and 400
200 and 500
Correct answer: 300 and 300
Correct answer: 200 and 400

6 Questions

Q1.
Which number in this equation is the minuend? 63 = 103 − 40
40
63
Correct answer: 103
Q2.
What is the difference between 190 and 210?
Correct Answer: 20, twenty
Q3.
Calculate the missing number in this equation: − 30 = 60
Correct Answer: 90, ninety
Q4.
Calculate the missing number in this equation: 63 − = 20
Correct Answer: 43, forty three
Q5.
Match up the differences with the correct expression to complete each equation.
Correct Answer:26 =,36 − 10

36 − 10

Correct Answer:46 =,66 − 20

66 − 20

Correct Answer:64 =,84 − 20

84 − 20

Correct Answer:34 =,44 − 10

44 − 10

Q6.
Sylvie the snail creeps 130 cm towards home. She still has 105 cm to go before she gets there. How many cm will she have travelled altogether? cm
Correct Answer: 235, two hundred and thirty five, 235cm, 235 cm