Mathematics
Subtraction
Educator section
Memorandum
Leaner section
Content
Activity: to calculate by choosing methods that are appropriate for solving problem [lo 1.8.1]
1. You have already been exposed to a variety of methods for doing subtraction. Now you have to see whether you are able to use your accumulated knowledge meaningfully. Calculate the following, using whatever method you prefer:
1.1 721 435 – 342 668
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1.2 834 206 – 467 937
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1.3 1 000 000 – 386 249
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2. Check your answers by using a pocket calculator.
Time for self-assessment
Let’s see how you are doing! Indicate how you feel about the different methods of subtraction. Colour the faces that reflect your feelings.
| Help! | Struggling | Almost coping | No problems | |
| I can subtract by counting backwards (LO 1.8) | _____________ | ____________ | _____________ | _____________ |
| I can use the rule of compensation for subtraction correctly (LO 1.8) | _____________ | ____________ | _____________ | _____________ |
| I know how to subtract with negative numbers (LO 1.8) | _____________ | ____________ | _____________ | _____________ |
| I can use the short method for subtraction (LO 1.8) | _____________ | ____________ | _____________ | _____________ |
Assessment
Learning Outcome 1: The learner will be able to recognise, describe and represent numbers and their relationships, and to count, estimate, calculate and check with competence and confidence in solving problems.
Assessment Standard 1.8: We know this when the learner estimates and calculates by selecting and using operations appropriate to solving problems that involve:
1.8.1: rounding off to the nearest 5, 10, 100 or 1 000.