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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
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
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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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:
Not at all | Fairly well | Well | Really well | |
I know what “sum of” means. | _______ | _______ | _______ | _______ |
I can explain the word “inverse”. | _______ | _______ | _______ | _______ |
I can group numbers to add them more easily. (LO1.8) | _______ | _______ | _______ | _______ |
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.
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