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Number concept, addition and subtraction


Educator section


1.1 xi

1.2 xv

1.3 watches


2.1 XLII

2.2 XCIX

2.3 MMDL


3.1 608

3.2 65

3.3 3 257

4. Will differ from year to year

Brain teaser

1. Move “minus” to just before “x” so that sum reads 1 x 1 = 1

2. Take one away from = and add to – so that sum reads 1 = 111 – 11

Leaner Section


Activity: to describe and illustrate different cultures' ways of writing [lo 1.2]

  • Can you deduce from this how the Romans would have written 11?


1.2 How would they have written 15?


1.3 Where are these Roman numerals still used nowadays?


  • Look carefully at the following:
We: 10 20 30 40 50 60 70 80 90 100
We: 100 200 300 400 500 600 700 800 900 1 000

2. Use the information given above and calculate the following.

Write your answers in Roman numerals:

  • 40 + 2 ________________________________________________________

2.2 90 + 9 ________________________________________________________

2.3 2 000 + 500 + 50 _______________________________________________

3. You have just practised writing like the Romans. Below are more examples of how they would write certain numbers. Can you write them in ordinary (our) numbers?

3.1 DCVIII ________________________________________________________

3.2 LXV ________________________________________________________

3.3 MMMCCLVII __________________________________________________

4. Write our present date in Roman numerals.


The matches below have been set out in Roman numerals, but the answers are incorrect. Can you “fix” each sum, so that the answer is correct, by moving only ONE match?


Evaluate yourself on a scale of 1 - 4 by just drawing a circle around the figure that is true about yourself.

I can Not at all Some-times Most of the time Always
Use the constant function of my pocket calculator for repeated addition 1 2 3 4
Write down Roman numerals for our numbers 1 2 3 4
Add and give the answer in Roman numerals 1 2 3 4
Write Roman numerals in ordinary numbers 1 2 3 4

However, the Roman counting system gets very complicated. The decimal system (OR METRIC SYSTEM) that we use is more practical. Let us consider the different ways in which we can add.


  • The answer of an addition sum is called the SUM OF THE TWO NUMBERS.
  • The INVERSE (reverse) calculation of addition is SUBTRACTION.


The order in which numbers are added makes no difference to the answer.

For example: 5 + 4 = 4 + 5
9 = 9
As well as: (16 + 14) + 12 = 16 + (14 + 12)
30 + 12 = 16 + 26
42 = 42


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 1.2: We know this when the learner describes and illustrates various ways of writing numbers in different cultures (including local) throughout history.

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Source:  OpenStax, Mathematics grade 5. OpenStax CNX. Sep 23, 2009 Download for free at http://cnx.org/content/col10994/1.3
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