New
New
Year 6

Explain how to balance equations with subtraction expressions

I can explain how to balance equations with subtraction expressions.

New
New
Year 6

Explain how to balance equations with subtraction expressions

I can explain how to balance equations with subtraction expressions.

Lesson details

Key learning points

  1. If the minuend and subtrahend are changed by the same amount, the difference stays the same.
  2. If you increase or decrease the minuend, the difference increases or decreases by the same amount.
  3. If you increase the subtrahend then the difference decreases.
  4. If you decrease the subtrahend then the difference increases.

Common misconception

Pupils immediately calculate expressions instead of considering the relationship between expressions.

Take time to model interrogation of values within expressions, identifying relationships between them. Encourage this reasoning and show how it can be more efficient than calculation especially in situations with larger values.

Keywords

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

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

  • Expression - An expression contains one or more values, where each value is separated by an operator.

Letters are used to represent an unknown in this lesson, which pupils may be less familiar with. Take time to show pupils that any letter can be used to represent an unknown value. Letters from the start or end of the alphabet are more commonly used.
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.
Which of the following expressions has the same sum as 306 + 30? Can you reason without calculating?
Correct answer: 300 + 36
Correct answer: 310 + 26
305 + 29
306 + 32
Q2.
Round 23,654 to the nearest multiple of 10
Correct Answer: 23,650
Q3.
Use an efficient strategy to calculate 56.75 + 22.25 =
Correct Answer: 79
Q4.
Use the correct inequality symbol to make this correct: 349,207 349,086
Correct Answer: >
Q5.
Use rounding, estimating, comparing or reasoning to determine the missing symbol in this inequality statement. 36 + 23 23 + 47
Correct Answer: <
Q6.
Use an efficient strategy to calculate 10,000 − 8,655 =
Correct Answer: 1,345

6 Questions

Q1.
Select the correct symbol to compare the expressions. 40.36 − 21.63 ___ 39.86 − 27.91
<
Correct answer: >
Q2.
Select the correct symbol to compare the expressions. 12,453 − 6,104 ___ 27,896 − 19,317
Correct answer: <
>
Q3.
The unknown subtrahend in the diagram below is
An image in a quiz
Correct Answer: 105
Q4.
Use an efficient strategy to calculate the unknown value g in g − 26,100 = 47,865 − 28,300
Correct Answer: 45,665
Q5.
Use an efficient strategy to calculate the unknown value g in 46.5 − 12.6 = 107.9 − g
Correct Answer: 74
Q6.
Izzy begins with 350 g of plasticine and removes 125 g. Jun begins with an unknown mass of plasticine and removes 90 g. Now they have the same mass of plasticine. How much did Jun begin with? g
Correct Answer: 315