New
New
Year 10
Foundation

Checking and securing understanding of calculations involving negative numbers

I can evaluate calculations involving positive and negative integers.

New
New
Year 10
Foundation

Checking and securing understanding of calculations involving negative numbers

I can evaluate calculations involving positive and negative integers.

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Lesson details

Key learning points

  1. Addition of negative integers can be made easier by considering zero pairs.
  2. Subtractions can all be re-written as additions of the additive inverse.
  3. The rules for multiplying with negative numbers can be extended to division.

Keywords

  • Additive inverse - The additive inverse of a number is a number that, when added to the original number, gives the sum of 0.

  • Absolute value - The absolute value of a number is its distance from zero. E.g. 5 and (−5) are both 5 away from zero and so both have an absolute value of 5

Common misconception

That addition will always make the result bigger.

If pupils are struggling with the concept that adding can make an integer smaller encourage them to use counters and form zero pairs.

Get pupils into pairs or groups. Each has a bag containing positive and negative counters. They take it in turns to take out some counters without looking and have to say if the answer will be positive or negative, whilst the others check.
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.
Calculate $$10^2 + 8^2$$
Correct Answer: 164
Q2.
Calculate $$9^2 + 8^2$$
Correct Answer: 145
Q3.
Which is the best estimate for $$\sqrt{38}$$ (to 1 decimal place)?
Correct answer: 6.2
6.6
5.9
Q4.
Which is the best estimate for $$\sqrt{40}$$ (to 1 decimal place)?
6.6
6.9
Correct answer: 6.3
Q5.
Which is the best estimate for $$\sqrt{50}$$ (to 1 decimal place)?
Correct answer: 7.1
6.9
7.5
Q6.
Calculate $$8^2 + 7^2$$
Correct Answer: 113

6 Questions

Q1.
Calculate $$-3 + 12$$
Correct Answer: 9
Q2.
Calculate $$-3 \times 12$$
Correct Answer: -36
Q3.
Calculate $$3 \times -12$$
Correct Answer: -36
Q4.
Calculate $$-3 \times -12$$
Correct Answer: 36
Q5.
Calculate $$12 \div -3$$
Correct Answer: -4
Q6.
Calculate $$-12 \div -3$$
Correct Answer: 4