1. Home
  2. Mathematics grade 7
  3. Term 3
  4. Division by multiples of 10

3.6 Division by multiples of 10

<< Chapter < Page
  Mathematics grade 7   Page 1 / 1
Chapter >> Page >

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

calculate molarity of NaOH solution when 25.0ml of NaOH titrated with 27.2ml of 0.2m H2SO4
Gasin Reply
what's Thermochemistry
rhoda Reply
the study of the heat energy which is associated with chemical reactions
Kaddija
How was CH4 and o2 was able to produce (Co2)and (H2o
Edafe Reply
explain please
Victory
First twenty elements with their valences
Martine Reply
what is chemistry
asue Reply
what is atom
asue
what is the best way to define periodic table for jamb
Damilola Reply
what is the change of matter from one state to another
Elijah Reply
what is isolation of organic compounds
IKyernum Reply
what is atomic radius
ThankGod Reply
Read Chapter 6, section 5
Dr
Read Chapter 6, section 5
Kareem
Atomic radius is the radius of the atom and is also called the orbital radius
Kareem
atomic radius is the distance between the nucleus of an atom and its valence shell
Amos
Read Chapter 6, section 5
paulino
Bohr's model of the theory atom
Ayom Reply
is there a question?
Dr
when a gas is compressed why it becomes hot?
ATOMIC
It has no oxygen then
Goldyei
read the chapter on thermochemistry...the sections on "PV" work and the First Law of Thermodynamics should help..
Dr
Which element react with water
Mukthar Reply
Mgo
Ibeh
an increase in the pressure of a gas results in the decrease of its
Valentina Reply
definition of the periodic table
Cosmos Reply
What is the lkenes
Da Reply
what were atoms composed of?
Moses Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
<< Chapter < Page Page > Chapter >>

Read also:

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Mathematics grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11075/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Mathematics grade 7' conversation and receive update notifications?

Ask