New
New
Year 6

Solve calculations with missing parts

I can solve addition calculations with missing parts.

New
New
Year 6

Solve calculations with missing parts

I can solve addition calculations with missing parts.

Lesson details

Key learning points

  1. The change in the sum is equal to the change in the missing addend.
  2. To calculate the missing addend, the known addend must be subtracted from the sum.
  3. A bar model can be used to represent a calculation with a missing addend.

Common misconception

The children might be inclined not to look at previous equations to help them. They might not make use of the adjustments to the whole.

Practise some really simple versions. Start with 1 + 2 = 3 and then ask them to adjust 3 by a single-digit number. Write this underneath and then ask them which part has changed and by how much? How do they know?

Keywords

  • Equation - An equation is used to show that one number, calculation or expression is equal to another.

  • Unknown - An unknown is a quantity that has a set value but it is represented by a symbol or letter.

  • Whole - The whole is all the parts or everything, the total amount.

  • Part - A part is a piece or section of the whole.

The structure of the problems in these slides (provided that you use the commutative property of addition) is very similar so make use of the learning wall by drawing up comparison arrows and blank boxes so the structure is permanently on display.
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.
Tick the equivalent expressions.
Correct answer: 51 + 40 + 9
51 + 32 + 19
Correct answer: 50 + 42 + 8
51 + 42 + 19
Q2.
Tick the two numbers that are complements to 1,000
849
Correct answer: 233
245
474
Correct answer: 767
Q3.
Tick the two numbers that are decimal complements to 10
Correct answer: 7.67
8.49
Correct answer: 2.33
2.45
4.74
Q4.
What is the missing number in this equation? + 61 = 150
Correct Answer: 89
Q5.
What is the missing number in this equation? 26 + + 11 = 70
Correct Answer: 33
Q6.
What is the missing number in this equation? + 45 + 18 = 89 + 6
Correct Answer: 32

6 Questions

Q1.
Which of the following best describes an unknown?
The solution to a worded problem
Correct answer: A quantity that has a set value represented by a symbol or letter
An answer you give when you don’t know the answer
Q2.
What is the mass of the plasticine on the balance scale?
An image in a quiz
Correct Answer: 500 g, 500, 500 grams
Q3.
What is the mass of the plasticine on the balance scale?
An image in a quiz
Correct Answer: 400 g, 400
Q4.
Without using a written method, calculate the unknown value in the pair of equations shown.
An image in a quiz
Correct Answer: 57
Q5.
Without using a written method, calculate the unknown.
An image in a quiz
Correct Answer: 54,300
Q6.
Without using a written method, calculate the unknown value in the pair of equations shown.
An image in a quiz
Correct Answer: 6.72