New
New
Year 4
Pupils use strategies to make solving calculations more efficient
I can use strategies to make solving calculations more efficient.
New
New
Year 4
Pupils use strategies to make solving calculations more efficient
I can use strategies to make solving calculations more efficient.
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Lesson details
Key learning points
- Equivalent calculations can be used with the same difference or same sum to make calculations ‘easier’.
- A number line can be used to represent more efficient methods.
- Inverse, the relationship between addition and subtraction, can be used to solve missing number problems.
Keywords
Efficient - Working efficiently means finding a way to solve a problem quickly whilst also maintaining accuracy.
Equivalent - Two or more things have the same value.
Inverse - The opposite in effect. The reverse of.
Common misconception
When using adjustment (e.g. 456 − 199), pupils may forget to subtract or add 1 to both parts.
The emphasis of same difference can encourage children to ensure they have subtracted or added to both parts of the calculation. Clearly display the visuals in this lesson to support with this.
Pupils will benefit from being able to discuss the strategies they would use to answer each question posed throughout the lesson. These provide great opportunities to both scaffold and challenge thinking. Use of metacognitive talk is crucial in modelling the thinking involved in this.
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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Starter quiz
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6 Questions
Q1.
Which equations would it be most efficient to solve using column subtraction?
476 − 376 =
557 − 555 =
Q2.
Which equations could be more easily solved using a mental calculation?
352 + 287 =
388 + 165 =
Q3.
Alex is trying to calculate the sum of 214 and 497 Which hundreds number will be closest to his answer?
Q4.
What is the most efficient way to calculate 285 − 99 = ?
Start at 99 and count on to 285
Use column subtraction
Subtract 100 then subtract 1
Q5.
Look carefully at Alex’s column addition. Which of these statements about the sum is true?
The ones digit of the sum is incorrect.
The hundreds digit of the sum is incorrect.
The sum is correct.
Q6.
Look carefully at Alex’s column subtraction. Which of these statements about the difference is true?
The ones digit of the difference is incorrect.
The tens digit of the difference is incorrect.
The difference is correct.
Exit quiz
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6 Questions
Q1.
Which equations could be more easily solved using a mental calculation?
2,568 - 1,567 = ___
8,658 - 2,454 = ___
Q2.
Which equations would it be most efficient to solve using column subtraction?
1,758 - 10 = ___
Q3.
What is the most efficient way to calculate 1,745 − 199 = ?
Start at 199 and count on to 1,745
Use column subtraction
Subtract 1 from each number then find the difference
Q4.
4,004 - 10 =
Q5.
Complete the column addition. What number has been added to 3,065 to sum to 8,347?
Q6.
Complete the column subtraction. What is the missing whole?
