New
New
Year 6
Explore mental and written strategies to solve problems
I can explore written and mental strategies to solve problems.
New
New
Year 6
Explore mental and written strategies to solve problems
I can explore written and mental strategies to solve problems.
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Lesson details
Key learning points
- Looking at the numbers involved and using number-sense supports us to know which strategy is more efficient.
- A number line is a useful mental strategy when it is obvious what to add or subtract.
- When using a formal written method the concept of constant difference can be used to make the calculation easier.
Keywords
Difference - The difference is the result of subtracting one number from another. It is how much one number differs from another - represented by how far apart they are on a number line.
Efficient - Being efficient means finding a way to solve a problem quickly whilst also maintaining accuracy.
Common misconception
Children may automatically use a formal written algorithm.
What do you notice about the numbers? What would you add/subtract to get to the nearest multiple of (a power of 10)? Can you represent this on a number line?
Children may struggle to grasp the constant difference concept. Give lots of practice and represent the calculations on a number line to support children to grasp this concept.
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.
Match the equation to its sum.
1,000
1,001
1,003
1,005
999
Q2.
Match the equation to its sum.
50,000
60,000
70,000
75,000
100,000
Q3.
Use a number line to calculate and find the missing part. 1,398 + = 5,000
Q4.
Use the formal written column subtraction algorithm to calculate 3,976,301 − 1,432,100 =
Q5.
Use the formal written column subtraction algorithm to calculate
1,309,052 − 132,421 =
Q6.
Lucas and Aisha play a game. Lucas wins 390,512 points and Aisha wins 200,000 fewer points. How many points does Aisha win? points
Exit quiz
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6 Questions
Q1.
Use a number line to calculate
69,998 + ? = 100,000
20,002
30,001
30,003
40,002
Q2.
Use a number line to calculate
190,000 − 137,999 =
Q3.
By using the constant difference concept, calculate the difference: 2,000,000 − 409,371 =
Q4.
By using the constant difference concept, calculate the missing number: 1,000,000 − = 23,147
Q5.
Use the most efficient method to solve this problem. A library has 50,000 books and some are out on loan. There are 17,998 books remaining in the library. How many are out on loan?
Q6.
Use the most efficient method to solve this problem.
A lottery winner won £1,500,000 and spent 387,399. How much money did they have left? £