# 1.12 To calculate by selecting appropriate operations for solving

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## Memorandum

1. Look at the tenth didgit. If 5 or more, add one to hundreth number. If 4 or less the hundreth number stays the same. Replace tenth and one-numbers with nought.

2. hundreds

hundreds, tens and ones

3.1 8 000 8 000

3.2 47 200 47 000

3.3 150 500 151 000

3.4 3 409 200 3 409 000

3.5 5 631 000 5 631 000

i) R90 000

ii) R14 000

## Activity: to calculate by selecting appropriate operations for solving problems[lo 1.8.1]

1. In Grade 5 we saw repeatedly how important it was to round off correctly. Amongst other things, it can help us to estimate an answer quickly, without using pencil and paper.

## Rounding off

• Let's revise
• Explain to your friend how we round off to the nearest 100.

2. Try to complete the following on your own:

3. Complete the following table:

 number rounded off to the nearest 100 rounded off to the nearest 1 000 3.1 7 995 3.2 47 216 3.3 150 505 3.4 3 409 235 3.5 5 630 981

## Puzzle!

• Can you round off the following to the nearest 10 000?

i) __________________________________________________________________

Price R89 895

ii) __________________________________________________________________

Price R13 995

TIME FOR SELF-ASSESSMENT

How well do you understand the preceding work? Assess yourself on a scale of 1 to 4. Circle the appropriate code:

1 = needs attention

2 = fairly good

3 = very good

4 = excellent

 Criteria: Code I can read 7-digit numbers correctly. (LO 1.3) 1 2 3 4 I can write 7-digit numbers correctly in words. (LO 1.3) 1 2 3 4 I am able to determine the value of digits in a number correctly. (LO 1.4) 1 2 3 4 I understand the powers of 10 and can use them correctly. (LO 1.10) 1 2 3 4 I can round off correctly to the nearest 100. (LO 1.8) 1 2 3 4 I can round off correctly to the nearest 1 000. (LO 1.8) 1 2 3 4 I can round off correctly to the nearest 10 000. (LO 1.8) 1 2 3 4

## 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.

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