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If you are aware of the pattern in which 8; ..6; ..4; ..2; ..0; is repeated, and concentrate, you should be able to count in 8’s forever, without mistakes.

  • Now, work with a friend. Count in 8’s from 0 to 104 while your friend checks you on a calculator. Then swap over.

3.5 Now count backwards in 8’s from 104 to 0 while your friend checks you on a calculator.

Then swap over.

4. Multiples of 9

4.1 Do what Sue suggested. Write down the missing multiples of 9 in the flow diagram and look at the last digit of each one. Spot the pattern.

4.2 Counting in 9’s is the easiest of all! Now complete the table below.

1 2 3 4 5 6 7 8 9 10 11 12
× 9 9 18 27 90 99

4.3 Now count backwards in 9’s while a friend checks you on the calculator. Begin with 108.

Now you should feel comfortable when you count in 6’s; 7’s; 8’s and 9’s and you already know how to count in tens. Practise this with a friend, forwards and backwards.

TEST YOUR SKILLS

1. Complete the following by doing one column each day or all four columns in one day, or two columns per day, as your educator chooses:

(a) 7 × 4 =………… 6 × 8 =…………….. 8 × 9 =…………….. 2 × 8 =…………….
(b) 9 × 8 = 3 × 7 = 1 × 7 = 6 × 9 =
(c) 7 × 6 = 8 × 7 = 6 × 5 = 8 × 7 =
(d) 2 × 5 = 3 × 9 = 7 × 9 = 5 × 5 =
(e) 10 × 10 = 2 × 8 = 9 × 9 = 4 × 6 =
(f) 3 × 6 = 8 × 5 = 9 × 0 = 9 × 8 =
(g) 4 × 2 = 5 × 8 = 7 × 3 = 7 × 10 =
(h) 5 × 6 = 6 × 6 = 8 × 8 = 3 × 8 =
(j) 4 × 4 = 0 × 10 = 4 × 9 = 5 × 7 =
(k) 5 × 9 = 4 × 8 = 5 × 7 = 4 × 7 =
TOTAL: TOTAL: TOTAL: TOTAL:

2. Now write all those that you got wrong and write down a way of finding the correct answer for each of them.

Activity 2:

To do mental calculations involving multiplication of whole numbers [LO 1.9]

1. Now complete this flow diagram:

2. Ways of solving 7 x 8.

Example of solving 7 x 8.

  • 7 x 4 + 7 x 4 OR double (7 x 4)
  • 8 + 8 + 8 + 8 + 8 + 8 + 8
  • Counting in 8’s till you reach 7 x 8
  • 7 x 5 + 7 x 3 i.e. breaking up the 8 as we did previously
  • 2 x 8 + 5 x 8 i.e. breaking up the 7 to make it easier; I know 2 x 8 and 5 x 8
  • Double 3 x 8 + 8
  • 7 x 10 - 2 x 7Be sure that you know what you are doing!

3. Now take each one that bothers you, and find a way of reaching the answer without a calculator and write your solution in the table below.

My way of solving each problem:

e.g. 8 × 8 Double 4 × 8 =32 + 32 = 64
3 × 6 6 × 3 (I know my 3 times table) = 18

TEST YOUR SKILLS

  • Complete each of the following:

1.

2.

3.

4.

5.

6. Explain the link between 4 and 5.

7. Use what you have learnt in 4 and 5 to complete the following:

(a) 6 × 20 = (f) 40 × 20 =
(b) 7 × 70 = (g) 60 × 60 =
(c) 50 × 3 = (h) 50 × 80 =
(d) 9 × 70 = (j) 60 × 7 =
(e) 8 × 30 = (k) 90 × 50 =

Activity 3:

To estimate and calculate by selecting and using a range of techniques [LO 1.1, 1.8]

1. You have found ways of calculating answers of tables that you have not memorized. Now estimate the answer by rounding off. Estimations should be quick and easy, but they only give approximate answers. Then find ways of reaching the exact answer of the following sums and write down all your steps:

1.1 7 x 18

  • 24 x 6

Discuss your methods with other friends in your group.

1.3 36 x 54

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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Good
Read about ancient clocks like_ hour glass, water clock and sun dial for a quiz and hand on Activity in the class
Neha Reply

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Source:  OpenStax, Mathematics grade 4. OpenStax CNX. Sep 18, 2009 Download for free at http://cnx.org/content/col11101/1.1
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