1.10 To represent, recognise and compare numbers  (Page 2/2)

DID YOU KNOW?

We read 43 685 as:

forty three thousand, six hundred and eighty five

5. In our everyday lives it is also important to be able to say numbers correctly in words, because it will help us to compare numbers with one another. Write the following numbers in words:

5.1 23 918 _________________________________________________________

5.2 47 007 _________________________________________________________

6. A number line can also help you represent numbers more easily. You can "see" where they lie on the number line and compare them more easily. Study the number line below:

6.1 Which numbers are, omitted at A, B, C, D and E?

A: __________________________________________________________________

B: __________________________________________________________________

C: __________________________________________________________________

D: __________________________________________________________________

E: __________________________________________________________________

6.2 Now take turns with a friend to show where the following numbers will be on the number line. Use an arrow:

a) 8 979

b) 11 003

c) 12 250

d) 14 997

e) 16 016

7. It is important to calculate answers correctly. To do this, we must decide what to do. Decide how you are going to calculate the answer of each question. Then fill in the missing numbers. Then compare your work with that of a friend.

7.1 10 000 = ___________________________________________ thousands

7.2 10 000 = ___________________________________________ hundreds

7.3 10 000 = ___________________________________________ tens

7.4 6 × 10 × 10 × 10 × 10 = ______________________________________

7.5 500 × ________________________________________________ = 50 000

7.6 3 000 × _______________________________________________ = 30 000

7.7 26 567 is 10 000 less than _________________________________________

7.8 ________________________________________ is 10 000 more than 6 824

7.9 _________________________________________is 50 000 less than 53 612

7.10 15 000 lies exactly halfway between _______________________ and 20 000

LET’S REVISE!

DO YOU STILL REMEMBER?

If you are asked to round off 627 to the nearest 10, it simply is a different way of asking:

Is 627 nearer to 630 or to 620?

Let us have another look at the number line:

627 is nearer to 630. If we therefore round 627 off to the nearest 10, the answer will be 630.

NOTE THIS:

If the number is exactly halfway between two numbers, e.g. 625, we round it off to the higher number. The answer will therefore be 630.

LET’S REVISE MORE

Challenge

Are you able to complete the following?

1. Rounding off can help you to estimate answers quickly. In this way you can determine what an answer should be approximately. Use your existing knowledge of rounding off and complete:

Round off to the nearest 100:

1.1

a) 624 ___________________

b) 896 ___________________

c) 450 ___________________

d) 1 239 ___________________

Round off to the nearest 1 000:

1.2

a) 3 429 ___________________

b) 8 140 ___________________

c) 25 712 ___________________

d) 56 500 ___________________

1.3 True or False?

a) 249 rounded to the nearest 100, is 200 ____________________________

b) 587 rounded to the nearest 100, is 600_____________________________

c) 11 450 rounded to the nearest 1 000, is 11 000_______________________

d) 23 811 rounded to the nearest 1 000, is 24 000_______________________

Play this game

Work with a friend. Use playing cards from which the 10, Jack, Queen, King, Ace and Joker have been removed.

• Player A chooses any five cards and places them face up, e.g. 5 ; 7 ; 1 ; 2 ; 1
• Player B now has to arrange the cards to obtain the highest possible number, e.g. 75 321. Write it down.
• Then player B arranges the cards to obtain the lowest number possible, e.g. 12 357. Write it down.
• Next, player B calculates the difference between the 2 numbers with the help of a pocket calculator.
• Take turns to use all the cards in this way and compare your answers.
• Do you detect any pattern?

Time for self-assessment once more

At this stage we would like to know how YOU feel about the work we have done thus far. Be honest and colour in the right block!

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 1.3: We know this when the learner recognises and represents numbers in order to describe and compare them:

Assessment Standard 1.8: We know this when the learner estimates and calculates by selecting and using operations appropriate to solving problems;

Assessment Standard 1.9: We know this when the learner We know this when the learner performs mental calculations.