New
New
Year 6

Solve addition calculations mentally by using known facts

I can solve addition calculations mentally by using known facts.

New
New
Year 6

Solve addition calculations mentally by using known facts

I can solve addition calculations mentally by using known facts.

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Lesson details

Key learning points

  1. If I increase this addend by __ then the sum will increase by the same amount.
  2. If I decrease this addend by __ then the sum will decrease by the same amount.
  3. A balance beam can represent unequal expressions or inequalities.

Keywords

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

  • Adjustment - An adjustment is a change to a number using either subtraction or addition.

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

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

Common misconception

Pupils may find it hard to understand that recalculating the adjusted part is an unnecessary step.

Display two sets of workings side-by-side. In the 1st, show the adjusted part being recalculated. In the 2nd, show it without recalculating the part. Pupils will hopefully see that the solution emerges from both.

Number bonds to 100 and 1,000 are very useful here and always worth practising. They could be used as a basis for early morning work or you could verbally challenge the children as they're lining up for assembly. Remember, success breeds motivation!
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 is the missing number in this part-whole model?
An image in a quiz
Correct Answer: 628
Q2.
What is the missing number in this part-whole model?
An image in a quiz
Correct Answer: 0.73
Q3.
In digits, write the number being represented by the place value counters.
An image in a quiz
Correct Answer: 5,301.3, 5301.3
Q4.
What is the complement to 1 of 0.654?
0.355
Correct answer: 0.346
0.364
0.366
Q5.
What is the complement to 1 for 0.654?
Correct Answer: 0.346
Q6.
What is the unknown in this equation? 435,000 + = 425,000 + 16,000
Correct Answer: 26,000, 26000

6 Questions

Q1.
What does an equation show?
Numbers and operation symbols together.
It is another word for an expression.
Correct answer: That one number, calculation or expression is equal to another.
The solution to a problem.
Q2.
What known fact is most helpful in completing the following calculation in your head? 134 + 5 = 139
Correct answer: 4 + 5 = 9
101 + 8 = 109
100 + 30 = 130
100 + 5 = 105
Q3.
Find the missing number mentally (use jottings if needed). = 67.24 + 0.76
Correct Answer: 68
Q4.
Find the missing number mentally (use jottings if needed). 15.65 + 0.34 =
Correct Answer: 15.99
Q5.
Find the missing number mentally (use jottings if needed). 68,000 + 232,000 =
Correct Answer: 300,000, 300000
Q6.
Find the missing number mentally (use jottings if needed). = 456,000 + 31,000
Correct Answer: 487,000, 487000