3.4 Adding and subtracting of decimal fractions

Mathematics

Decimal fractions

Educator section

Memorandum

17.2 a) 999,955

1. 802,383
2. 115,749
3. 420,799

18. 0,1818181

0,8181818

0,9999999

Above-mentioned are repetitive fractions

Rounded off, 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

n) 8,6

o) 8,2

Leaner Section

Content

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.

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.

…………………………………………………………………………………………..

…………………………………………………………………………………………..

• You already know that 2 elevenths plus 9 elevenths = 11 elevenths = one !
• How do you explain the above answer?

…………………………………………………………………………………………..

…………………………………………………………………………………………..

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 = .................

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:

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 1.7: 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.