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LESSON 2: NUMBER SENTENCES
Self-assessment
Do the learners understand the work? Let them colour the faces that show what they can do.
REPRESENTING WHOLE NUMBERS Requirements
I can represent whole numbers in different ways.
I know the difference between even and odd numbers.
I can round off numbers to the nearest 5, 10, 100 and 1 000. Can the learners do it?
LESSON 2: NUMBER SENTENCES
Number sentences introduce operations with numbers (and in the senior and FET phases with variables). Once again, emphasise the concept using concrete, relevant examples.
Learners in the intermediate phase sometimes work with number sentences in isolation. However, it is more common for learners to combine number sentences with other forms of representation; for example, mathematical problems that are simplified in words, as well as numbers and calculations represented in flow charts.
It is important to include examples of mathematical problems that may be expressed as number sentences throughout the year. Also include number sentences in daily mental maths exercises.
You studied number sentences in Grade 4. In Grade 5, you will use number sentences to describe problems and solve number sentences through inspection and by trial and improvement.
Briefly revise the Grade 4 work.
What are number sentences?
A number sentence is an arrangement of numbers and symbols:
233 + 19 = 252 455 – 176 = 279 498 × 3 = 1 494 120 ÷ 2 = 60
You will not always work with number sentences. Sometimes a maths problem is expressed in words, and before you can solve it mathematically, you must first formulate a number sentence.
Example: Your swimming lessons cost R3 900. Your mom makes 12 equal payments. How much is each payment?
Start by reading the problem again and writing down the information:
Total amount for lessons: R3 900
How many payments? 12 equal payments
The question does not ask how much your mom paid in total, but how much she must pay each month (12 payments). Write down the number sentence:
Apply your Grade 4 calculation skills:
3 900 ÷ 12 = ?
. 3 2 5 1 2 3 9 0 0 - 3 6 3 0 - 2 4 6 0 - 6 0 0
It means your mom must make 12 equal payments of R325 each.
In this number sentence, we divided numbers.
You can also write a number sentence with + , – , × and ÷.
Example: Melanie has 36 blue marbles. Refilwe has 25 red marbles and 17 blue marbles. How many blue marbles do they have altogether?
36 + 17 = ?
If we want to solve the number sentence:
36 + 17 = 53
Melanie and Refilwe have 53 blue marbles altogether.
Write a few of your own number sentences.
