New
New
Year 7

Subtraction of positive and negative integers

I can use the mathematical structures that underpin subtraction to add and subtract positive and negative integers.

New
New
Year 7

Subtraction of positive and negative integers

I can use the mathematical structures that underpin subtraction to add and subtract positive and negative integers.

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Lesson details

Key learning points

  1. Any subtraction can be re-written as an equivalent addition.
  2. Subtracting a postive number is the same as adding a negative number.
  3. Subtracting a negative number is the same as adding a positive number.

Common misconception

Minus and a minus make a plus, 2 negatives make a positive, double negative makes a positive, etc.

The use of additive inverses should avoid this common misconception. Be aware that pupils maybe already be familiar with this statement.

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

The introduction to rewriting a subtraction as an equivalent addition requires correct use of mathematical language. Watching the video of the teacher explanation could help.
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).

Video

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6 Questions

Q1.
Complete the statement. The value of a number is its distance away from zero.
Correct Answer: absolute
Q2.
Which integer does this set of counters represent?
An image in a quiz
11
Correct answer: 3
-3
-11
Q3.
Work out: 9 + (-7) =
Correct Answer: 2, two
Q4.
Work out (-5) + (-3)
Correct answer: (-8)
(-2)
2
8
Q5.
Starting with the calculation with the lowest answer, sort these calculations in order of size from lowest answer to highest answer.
1 - (-3) + (-4)
2 - (-2) + (-1)
3 - 5 + (-5)
4 - 4 + (-2)
5 - (-3) + 7
Q6.
Work out: 10 + (-12) + 7 + (-6) =
Correct Answer: (-1), -1, - 1, (- 1)

6 Questions

Q1.
Complete the statement. The additive inverse of a number is a number that, when added to the original number, gives the sum of .
Correct Answer: 0, zero
Q2.
Match together each of these subtractions with its equivalent addition.
Correct Answer:6 - 4,6 + (-4)

6 + (-4)

Correct Answer:4 - 6,4 + (-6)

4 + (-6)

Correct Answer:6 - (-4),6 + 4

6 + 4

Correct Answer:(-4) - 6,(-4) + (-6)

(-4) + (-6)

Q3.
Match each calculation to its answer.
Correct Answer:6 - 4,2

2

Correct Answer:4 - 6,(-2)

(-2)

Correct Answer:6 - (-4),10

10

Correct Answer:(-4) - 6,(-10)

(-10)

Q4.
Work out (-5) - (-8)
-13
-3
Correct answer: 3
13
Q5.
Work out: (-1) + 2 - (-3) - 4 + (-5) =
Correct Answer: (-5), -5, - 5, (- 5)
Q6.
Complete the statement. The missing integer is
An image in a quiz
Correct Answer: (-4), -4, - 4, (- 4)