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20.1
a) 260
b) 2 600
c) 26,7
d) 267
e) 2 670
f) 26,79
g) 267,9
h) 2 679
20.2 x10: Each digit moves 1 place left / comma moves 1 to the right.
x100: Each digit moves 2 places left / comma moves 2 to the right.
x1000: Each digit moves 3 places left / comma moves 3 to the right.
20.4
| a) | 54,8 | 548 | 5480 |
| b) | 3,67 | 36,7 | 367 |
| c) | 8,9 | 89 | 890 |
| d) | 165,38 | 1653,8 | 16 538 |
| e) | 282,51 | 2825,1 | 28 251 |
20.5.1
a) 21,522
b) 46,215
c) 1,4
d) 4,64
e) 12 250
f) 2 370,6
x with number<1
20.8
a) 0,4964
b) 1,3737
c) 0,109
d) 5,53724
e) 38,57997
f) 16,78164
23.1 10: Comma moves 1 place left
Each digit moves 1 place right
100: Comma moves 2 place left
Each digit moves 2 place right
1000: Comma moves 3 places left
Each digit moves 3 places right
23.3
| 8,21 | 0,729 | 0,6 | ||||||
| 0,864 | 0,6254 | 0,0392 | 8,791 | 0,035 | 0,08 | |||
| 74,68 |
20. MULTIPLICATION OF DECIMAL FRACTIONS
20.1 Let us revise
Do the following with the help of your calculator:
| SUM | ANSWER | |
| e.g. | 2,6 x 10 | 26 |
| a) | 2,6 x 100 | ......................... |
| b) | 2,6 x 1 000 | ......................... |
| c) | 2,67 x 10 | ......................... |
| d) | 2,67 x 100 | ......................... |
| e) | 2,67 x 1 000 | ......................... |
| f) | 2,679 x 10 | ......................... |
| g) | 2,679 x 100 | ......................... |
| h) | 2,679 x 1 000 | ......................... |
20.2 Work in groups of three. Quickly formulate rules for the multiplication of decimal fractions by 10, 100 and 1 000.
20.3 Do you still remember?
10 x 1 = 10 = 101
10 x 10 = 100 = 102
10 x 10 x 10 = 1 000 = 103
10 x 10 x 10 x 10 = 10 000 = 104
10 x 10 x 10 x 10 x 10 = 100 000 = 105
10 x 10 x 10 x 10 x 10 x 10 = 1 000 000 = 106
20.4 Complete the following table:
| × | 10 1 | 10 2 | 10 3 | |
| e.g. | 3,2 | 32 | 320 | 3 200 |
| a) | 5,48 | ..................... | ..................... | ..................... |
| b) | 0,367 | ..................... | ..................... | ..................... |
| c) | 0,89 | ..................... | ..................... | ..................... |
| d) | 16,538 | ..................... | ..................... | ..................... |
| e) | 28,251 | ..................... | ..................... | ..................... |
20.5 More revision
20.5.1 Work with a friend. Calculate the answers without using a calculator:
a) s = 3,587 x 6
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b) f = 9,243 x 5
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c) p = 0,02 x 70
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d) r = 0,058 x 80
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e) t = 24,5 x 500
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f) h = 2,634 x 900
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20.5.2 Check your answers with a calculator.
20.6 MULTIPLYING DECIMAL FRACTIONS WITH DECIMAL FRACTIONS
20.6.1 Read the following problem and work through the different solutions with a friend:
A tortoise walks 0,8 km in 1 hour. How far will he walk in 0,6 of an hour?
a)
I convert the decimal fractions to proper fractions:
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