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Mathematics

Decimal fractions

Educator section

Memorandum

23.4.2 a) 0,041

  1. 0,81
  2. 0,0093
  • b en c

23.6 a) 1,234

  1. 0,845
  2. 7,23

25. a) R51

  1. R211,59
  2. 21160c
  3. R2,90
  4. Ja

Cost per call: R1,77

  1. 91,5
  2. R102,13
  3. R1,28 x 24 = R30,72
  4. R3,27
  5. Own answers

Leaner section

Content

Activity: division by multiples of 10 [lo 1.5.1, lo 1.7.5]

23.4 DIVISION BY MULTIPLES OF 10

23.4.1 Do you still remember?

a) This is how I divide 0,8 by 40:

0,8 ÷ 40 = (0,8 ÷ 10) ÷ 4

= 0,08 ÷ 4

= 0,02

b) When I divide 4,2 by 600, I say:

4,2 ÷ 600 = (4,2 ÷ 100) ÷ 6

= 0,042 ÷ 6

= 0,007

23.4.2 Calculate the following without a calculator:

a) j = 3,28 ÷ 80

…………………………………………………………………………………………..

…………………………………………………………………………………………..

b) d = 567 ÷ 700

…………………………………………………………………………………………..

…………………………………………………………………………………………..

c) g = 18,6 ÷ 2 000

…………………………………………………………………………………………..

…………………………………………………………………………………………..

23.5 DIVISION WITH DECIMAL FRACTIONS

23.5.1 Work through the following examples with a friend:

A roll of material is 11,25 m long. 1,5 m of material is needed to make one dress.

How many dresses can be cut from this roll of material?

a) I must calculate 11,25 ÷ 1,5

I change the decimal fractions to fractions:

11 , 25 = 11 25 100 = 11 1 4 size 12{"11","25"="11" { { size 8{"25"} } over { size 8{"100"} } } ="11" { { size 8{1} } over { size 8{4} } } } {} en 1,5 = 1 5 10 = 1 1 2 size 12{1,5=1 { { size 8{5} } over { size 8{"10"} } } =1 { { size 8{1} } over { size 8{2} } } } {}

11 1 4 ÷ 1 1 2 = 45 4 ÷ 3 2 45 4 × 2 3 7 1 2 alignl { stack { size 12{"11" { { size 8{1} } over { size 8{4} } } div 1 { { size 8{1} } over { size 8{2} } } = { { size 8{"45"} } over { size 8{4} } } div { { size 8{3} } over { size 8{2} } } } {} #= { { size 8{"45"} } over { size 8{4} } } times { { size 8{2} } over { size 8{3} } } {} # =7 { { size 8{1} } over { size 8{2} } } {}} } {}

I make use of equivalent fractions :

11 , 25 ÷ 1,5 = 11 , 25 1,5 × 10 10 = 112 , 5 15 7,5 7 1 2 alignl { stack { size 12{"11","25" div 1,5= { { size 8{"11","25"} } over { size 8{1,5} } } times { { size 8{"10"} } over { size 8{"10"} } } = { { size 8{"112",5} } over { size 8{"15"} } } } {} #=7,5 {} # =7 { { size 8{1} } over { size 8{2} } } ` {}} } {}

c) I must calculate 11,25 ÷ 1,5I change the divisor to a whole number so that I can divide easier.

1,5 × 10 = 15

To keep the balance in the sum, I must also multiply the dividend by 10!

11,25 × 10 = 112,5

7 ,5
15 112 ,5
–105
7 5
–7 5
· ·

The answer is thus 7,5 dresses..

23.5.2 Which of the above-mentioned methods are precisely the same?

…………………………………………………………………………………………..

…………………………………………………………………………………………..

23.5.2 Which of the above-mentioned methods are precisely the same?

23.6 Calculate the following by first changing the divisor to a whole number:

a) q = 0,88848 ÷ 0,72

…………………………………………………………………………………………..

…………………………………………………………………………………………..

…………………………………………………………………………………………..

…………………………………………………………………………………………..

b) p = 0,14365 ÷ 0,17

…………………………………………………………………………………………..

…………………………………………………………………………………………..

…………………………………………………………………………………………..

…………………………………………………………………………………………..

c) v = 0,30366 ÷ 0,042

…………………………………………………………………………………………..

…………………………………………………………………………………………..

…………………………………………………………………………………………..

…………………………………………………………………………………………..

24. Time for self-assessment

  • Tick the applicable block:
YES NO
I can divide decimal fractions by 10 correctly.
I can divide decimal fractions by 100 correctly.
I can divide decimal fractions by 1 000 correctly.
I know how to divide decimal fractions by multiples of 10.
I can divide decimal fractions by decimal fractions.

25. Look at the following telephone account and answer the questions. You may use your calculator.

a) Round off the cost of the overseas call to the nearest rand. ……………………

b) What is the total cost of the calls that were made? …………………………….

c) Round off the above answer to the nearest cent. ………………………………

d) What was the average cost of each cell phone (Vodacom) call? ………………

e) Is MTN cheaper than Vodacom? ……………….. Motivate. ………………...

…………………………………………………………………………………………..

…………………………………………………………………………………………..

f) Round off the cost of the national calls (0 – 50 km) to 1 digit after the comma.

…………………………………………………………………………………………..

g) What is the total cost of the national calls? ……………………………………

h) If two “ShareCall” calls cost R1,28, what would 48 such calls cost?

…………………………………………………………………………………………..

i) The account is paid with a R200 note and a R20 note. How much change will be given?

…………………………………………………………………………………………..

j) How much is YOUR telephone account each month, on average, over a period of one year?

…………………………………………………………………………………………..

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 1.5: We know this when the learner solves problems in context including contexts that may be used to build awareness of other Learning Areas, as well as human rights, social, economic and environmental issues such as:

1.5.1 financial (including profit and loss, budgets, accounts, loans, simple interest, hire purchase, exchange rates);

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

1.7.5 division of positive decimals with at least 3 decimal places by whole numbers.

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Mathematics grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11075/1.1
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