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MathidiaMathematics Academy
Calculations and problem solving
Lesson 11 of 75
Introduction

Mental calculation strategies

Objective. Use compensation, partitioning and known facts efficiently.

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

Learn: the key idea

Mental calculation strategies is built on a small number of dependable facts. Choose efficient operations and reason through multi-step situations. 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 67 + 48.

-178335882107132+48
Number line from -17 to 132 with a jump of 48 forwards from 67
  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: 115.

Answer: 115

Concept mastery

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

Complete a practice set to see your concept breakdown here.

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.

Start practising

Common mistake. A common mistake in mental calculation strategies 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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