1.19 To calculate by selecting operations appropriate to solving

Mathematics

Number concept

Educator section

Memorandum

1.1 3 272 + 128 = 3 400

1 154 + 136 = 1 290

1 103 + 97 = 1 200

SUM = 5 890

1.2 138 + 622 = 760

259 + 11 011 = 11 270

235 + 25 = 4 260

SUM: = 16 290

2.1 Wrong: 640 + 360 + 5 + 2 – 2 = 1 005

2.2 Wrong: 2 500 + 360 = 2 880

Brain Teaser

1. 41 186 + 23 880 + 12 = 65 078

2. 758 817 + 100 + 118 200 – 4 = 875 113

Various other possibilities

Leaner section

Content

Activity: to calculate by selecting operations appropriate to solving problems [lo 1.8.2]

Do you still remember?

Addition is easier when we GROUP numbers.

Look carefully at the following example:

37 + 28 + 12 + 16 + 13 + 44

If we group the numbers they look like this: 37 + 13 = 50

28 + 12 = 40

44 + 16 = 60

SUM = 150

Understand? We group the numbers like this because we want to “complete” the tens, so that it is easier to add.

1. Group the following numbers so that you can add them more easily:

1.1 3 272 ; 1 154 ; 97 ; 128 ; 136 ; 1 103

_________________ + _________________ = _________________

_________________ + _________________ = _________________

_________________ + _________________ = _________________

SUM = _________________

1.2 138 ; 259 ; 4 235 ; 25 ; 11 011 ; 622

_________________ + _________________ = _________________

_________________ + _________________ = _________________

_________________ + _________________ = _________________

SUM = _________________

2. Work with a friend and determine whether the answers of the following calculations are correct. If they are not, indicate the error.

2.1 638 + 367 = 640 + 360 – 5 = 995

2.2 2 496 + 364 = 2 600 + 360 = 2 960

Brain teaser!

You are supposed to complete the following with a calculator, but the 9 on your calculator doesn’t work! How will you solve the problem? Write down everything you key in and calculate the answer:

1. 41 186 + 23 892

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2. 756 917 + 118 196

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Time for self-assessment

How do you feel about the work so far? Please give us some indication of how you feel about the work that we have completed by now. Make a tick in the appropriate column:

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:

1.8.2: addition and subtraction of whole numbers.