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MathidiaMathematics Academy
Integers and negative numbers
Lesson 9 of 75
Challenge

Subtract directed numbers

Objective. Subtract integers, including subtracting a negative.

  1. 1. Learn
  2. 2. Worked example
  3. 3. Practice
  4. 4. Feedback
  5. 5. Continue

Learn: the key idea

Subtract directed numbers is built on a small number of dependable facts. Model directed number and calculate across zero. Represent the information first, choose a method deliberately, show each step and use an inverse operation or estimate to check that the result fits the question.

Worked example

Work out −5 − 8.

-4-2-11346−8
Number line from -4 to 6 with a jump of 8 backwards from 5
  1. 1Identify the mathematical information and what must be found.
  2. 2Represent it with a number line, diagram, table or expression where helpful.
  3. 3Apply the relevant fact carefully and keep each line clear.
  4. 4Check the result against the conditions in the question: -13.

Answer: -13

Concept mastery

Based on your past attempts at this lesson — the question types to practise again come first.

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Practice

Practice happens on its own screen, one question at a time. Answers stay hidden until you submit yours, and you can stop and pick up at the same question later.

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Common mistake. A common mistake in subtract directed numbers is to apply a remembered procedure before reading the signs, units or order carefully. Write the structure first, then calculate and check.

Your progress

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