New
New
Year 6

Solve problems explaining which strategy is most efficient

I can solve problems, explaining which strategy is most efficient.

New
New
Year 6

Solve problems explaining which strategy is most efficient

I can solve problems, explaining which strategy is most efficient.

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Lesson details

Key learning points

  1. We know different strategies for addition and subtraction including mental and written strategies.
  2. Looking at the numbers helps us see which strategy is most efficient.
  3. Missing number problems can be rearranged to identify an efficient strategy to solve the problem.

Keywords

  • Subtrahend - The subtrahend is the number to be subtracted. It is the second number in a subtraction.

  • Efficient - Being efficient means finding a way to solve a problem quickly whilst also maintaining accuracy.

Common misconception

Children may automatically resort to the use of the formal column algorithms. These are not always the most efficient methods.

What do you notice about the numbers? Is there a mental strategy that you could use?

Children need to be encouraged to slow down and look at the numbers in each calculation and to reason about which strategy they would use and to reason about why.
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.
Use an efficient method to find the sum of 14,875 and 3,123
Correct Answer: 17,998
Q2.
Use an efficient method to find the sum of 9,308 and 5,245
Correct Answer: 14,553
Q3.
Match the expression to the correct difference.
Correct Answer:750,000 − 45,000,705,000

705,000

Correct Answer:750,000 − 50,000,700,000

700,000

Correct Answer:750,000 − 30,000,720,000

720,000

Correct Answer:750,000 − 75,000 ,675,000

675,000

Correct Answer:750,000 − 55,000 ,695,000

695,000

Q4.
Use a number line to calculate 50,000 − 34,995 =
Correct Answer: 15,005
Q5.
Use the ‘constant difference’ strategy to calculate 15,000 − 2,375 =
Correct Answer: 12,625
Q6.
Two numbers have a total of 367,200 If one of the numbers is 320,000 what is the other number?
Correct Answer: 47,200

6 Questions

Q1.
Match these expressions to the strategy you would use to calculate them.
Correct Answer:1,359,903 + 45,908 ,column addition

column addition

Correct Answer:1,359,903 + 210,000,partitioning

partitioning

Correct Answer:90,000 − 29,998,number line

number line

Correct Answer:400,000 − 168,993,constant difference then column subtraction

constant difference then column subtraction

Correct Answer:2,328,992 − 168,445,column subtraction

column subtraction

Q2.
A charity needs to raise £200,000 and it has already raised £57,306 Which strategy is most efficient to use to calculate how much more money it needs to raise?
Column addition
Column subtraction
Partitioning
Number line
Correct answer: Constant difference
Q3.
A charity raises £246,803 in a fundraising event. It then raises another £1,907,368 Which strategy is most efficient to use to calculate how much money it has raised in total?
Correct answer: Column addition
Column subtraction
Partitioning
Number line
Constant difference
Q4.
Find the missing number in this equation. 508,914 = + 205,730
Correct Answer: 303,184
Q5.
Calculate the multi-step equation. Think about the strategy which will be most efficient. 205,677 + 499,998 − 200,000 =
Correct Answer: 505,675
Q6.
Two numbers have a total of 1,690,768 and a difference of 999,412 What are the two numbers? 345,678 and
Correct Answer: 1,345,090