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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

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 to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
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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