OpenStax-CNX module: m31262
1
Adding and subtracting of decimal
fractions
∗
Siyavula Uploaders
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†
Creative Commons Attribution License 3.0
1 MATHEMATICS
2 Decimal Fractions
3 EDUCATOR SECTION
4 Memorandum
17.2 a) 999,955
a) 802,383
b) 115,749
c) 420,799
18. 0,1818181
0,8181818
0,9999999
Above-mentioned are repetitive fractions
Rounded o, the answer is 1.
19.
a) 1
b) 3,3
c) 0,67
d) 4,3
e) 6,4
f) 2,7
g) 3,4
h) 1,25
i) 1,05
j) 6,7
k) 2,98
l) 1,12
m) 5
∗ Version
1.1: Aug 12, 2009 7:18 am -0500
† http://creativecommons.org/licenses/by/3.0/
http://cnx.org/content/m31262/1.1/
OpenStax-CNX module: m31262
2
n) 8,6
o) 8,2
Leaner Section
5 Content
5.1 ACTIVITY: Adding and subtracting of decimal fractions [LO 1.7.4]
17. ADDING AND SUBTRACTING OF DECIMAL FRACTIONS:
17.1 Do you still remember?
It is very easy to add and subtract decimal fractions. We do it in exactly
the same way that we would add and subtract whole numbers.
Just be certain that you write:
• the tenths in the tenths column.
• the hundredths in the hundredths column.
• the thousandths in the thousandths column.
Figure 1
17.2 Calculate:
a) n = 284,523 + 715,432
b) d = 476,897 + 325,486
c) k = 532,298 416,549
d) b = 785,361 364,562
18. BRAIN-TEASER!
• Write two elevenths as a decimal fraction. Then write nine elevenths as a decimal fraction. Add the
two answers together.
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• You already know that 2 elevenths plus 9 elevenths = 11 elevenths = one !
• How do you explain the above answer?
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19. Let us see how you do in the following mental test.
a) 0,6 + 0,4 = .................
b) 2,4 + 0,9 = .................
c) 0,27 + 0,4 = .................
d) 5 0,7 = .................
e) 3,8 + 2,6 = .................
http://cnx.org/content/m31262/1.1/
OpenStax-CNX module: m31262
3
f) 3,2 0,5 = .................
g) 3,45 0,05 = .................
h) 3,45 2,2 = .................
i) 3,45 2,4 = .................
j) 2,65 + 4,05 = .................
k) 4 1,02 = .................
l) 0,39 + 0,73 = .................
m) 3,25 + 1,75 = .................
n) 4,9 + 3,7 = .................
o) 12 3,8 = .................
• Complete by ticking the applicable block:
MYMARKS
IMPROVED
GOT THE SAME RESULT
DID WORSE
when I compare my results with
the results of the previous mental
test.
Table 1
6 Assessment
The learner will be able to recognise, describe and represent numbers and their
relationships, and to count, estimate, calculate and check with competence and condence in solving problems.
Assessment Standard 1.7: We know this when the learner estimates and calculates by selecting and
using operations appropriate to solving problems that involve:
1.7.4 addition, subtraction and multiplication of positive decimals to at least 2 decimal places.
Learning Outcome 1:
http://cnx.org/content/m31262/1.1/