3.5 Multiplication of decimal fractions  (Page 2/2)

Thus he walks 0,48 km.

b) I first work out what 8 × 6 is. The answer is 48. Now I add up the amount of decimal places after each comma. There are 2. Thus, my answer must have 2 digits after the decimal comma.

The answer is thus 0,48.

20.6.2 What do you notice when you compare the answer (product) with the multiplicand?

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Can you explain this?

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20.7 REMEMBER!

20.8 Calculate the following on your own without a calculator:

a) j = 0,146 x 3,4

b) v = 2,41 x 0,57

c) u = 0,025 x 4,36

d) g = 8,143 x 0,68

e) d = 7,293 x 5,29

f) o = 3,849 x 4,36

21. Time for self-assessment

22. Let us play a game.

You need a friend and a calculator for this game.

Key in any decimal number on your calculator.

Then divide it by 10, 100 or 1 000. Give the calculator to your friend. He/She must get the original number again.

e.g. Player 1 keys in : 43,674.

Player 1 divides 43,674 by 1 000 and gets 0,043674.

Player 2 must get 43,674 on the screen.

Player 2 must thus × by 1 000!

23. DIVISION BY DECIMAL FRACTIONS

Let us first revise.

23.1 Divide into groups of 3. Can you explain to each other what happens when we divide natural and decimal numbers by 10, 100 and 1 000?

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23.2 Take turns in saying the answers of the following to each other, out aloud.

a) 6 ÷ 10

b) 0,3 ÷ 10

c) 0,06 ÷ 100

d) 2,9 ÷ 100

e) 4 ÷ 100

f) 15,8 ÷ 100

g) 8 ÷ 1 000

h) 39,2 ÷ 100

i) 34,67 ÷ 1 000

j) 27,458 ÷ 10

23.3 Colour the answers to find the correct “path” to the house!

a) 82,1 ÷ 10

b) 86,4 ÷ 100

c) 746,8 ÷ 10

d) 625,4 ÷ 1 000

e) 39,2 ÷ 1 000

f) 72,9 ÷ 100

g) 879,1 ÷ 100

h) 6 ÷ 10

i) 35 ÷ 1 000

j) 8 ÷ 100

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, classifies and presents the following numbers in order to describe and compare them:

1.3.4 numbers in exponential form including squares of natural numbers to at least 12 ² , cubes of natural numbers to at least 5 ³ , and their square and cube roots;

Assessment Standard 1.7: We know this when the learner estimates and calculates by selecting and using operations appropriate to solving problems that involve:

1.7.7 rounding off numbers to at least one decimal place;

Assessment Standard 1.9: We know this when the learner uses a range of techniques to perform calculations including:

1.9.2 using a calculator;

Assessment Standard 1.10: We know this when the learner uses a range of strategies to check solutions and judges the reasonableness of solutions.

Learning Outcome 2: The learner will be able to recognise, describe and represent patterns and relationships, as well as to solve problems using algebraic language and skills.

Assessment Standard 2.3: We know this when the learner represents and uses relationships between variables in a variety of ways using:

2.3.3 tables.