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BRAIN-TEASER!

Calculate the following in the same way as the Egyptians did thousands of years ago:

15 × 241

  • Is there an easier way of doing it? Discuss this with your friend. Check your answer with a calculator.

DID YOU KNOW?

Thus we can also make use of DOUBLING when we want to multiply:

2 × 280 = (200 + 200) + (80 + 80)

= 400 + 160

= 560

Activity 5:

To use a series of techniques to do computations with whole numbers [lo 1.10.4]

1. If you looked carefully at the example above, you would have seen that this method of doubling differs from that of the Egyptians. Can you calculate the following by doubling it in exactly the same way?

1.1 2 × 1 430 =

1.2 2 × 2 315 =

2. We would very much like to use the shortest possible method in Mathematics, because it saves a lot of time, trouble and paper. Calculate the product again by doubling, but this time use a shorter method if you can.

2.1 2 × 14 820 =

2.2 2 × 36 947 =

3. There is another technique that you can use to calculate the product. You can double and halve ! This makes it easier to multiply with the “big” numbers. Look carefully at the following:

126 × 5= 63 × 10 (halve 126 ; double 5)= 630

Can you find the following answers by doubling and halving ?

3.1 50 × 24 3.2 5 × 346

BRAIN-TEASER!

Can you fill in the missing numbers/factors WITHOUT using your calculator?

48 × 12 = 576 64 × 10 = 640
........... × 24 = 576 32 × ........... = 640
12 × ........... = 576 ........... × 40 = 640
6 × ........... = 576 8 × ........... = 640
........... × ........... = 576 ........... × ........... = 640

Did you discover a pattern?

Activity 6:

To calculate by using selected computations [lo 1.9.2]

1. Now let us look at multiplication with multiples of 10 and 100. As we work through the examples, you will see that there are certain rules that you must follow in order to calculate the product. If you apply these rules, you will be able to calculate the answers without doing long computations on paper. Work with a friend and write down the product of the following:

1.1 10 × 6 = ......................... ; 10 × 60 = ......................... ;

10 × 600 = ......................... and 10 × 6 000 = .........................

1.2 10 × 9 = ......................... ; 10 × 90 = ......................... ;

10 × 900 = ......................... and 10 × 9 000 = .........................

1.3 10 × 15 = ......................... ; 10 × 150 = ......................... ;

10 × 1 500 = .........................

1.4 10 × 26 = ......................... ; 10 × 260 = ......................... ;

10 × 2 600 = .........................

Can you now write down a rule for multiplying any number by 10?

Does this “work” for 0,5 × 10?

2. Let us look at multiplication with multiples of 100. Work with the same friend and write down the product of:

2.1 100 × 8 = ......................... ; 100 × 80 = ......................... ;

100 × 800 = .........................

2.2 100 × 13 = ......................... ; 100 × 130 = ......................... ;

100 × 1 300 = .........................

2.3 100 × 27 = ......................... ; 100 × 270 = ......................... ;

Questions & Answers

the diagram of the digestive system
Assiatu Reply
allimentary cannel
Ogenrwot
How does twins formed
William Reply
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
what is genetics
Josephine Reply
Genetics is the study of heredity
Misack
how does twins formed?
Misack
What is manual
Hassan Reply
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
Joseph Reply
what is biology
Yousuf Reply
the study of living organisms and their interactions with one another and their environments
AI-Robot
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
Joseph Reply
what is the blood cells
Shaker Reply
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
Abdullahi Reply
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
Ramadan
What is classification
ISCONT Reply
is organisms that are similar into groups called tara
Yamosa
in what situation (s) would be the use of a scanning electron microscope be ideal and why?
Kenna Reply
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
cell is the building block of life.
Condoleezza Reply
what is cell divisoin?
Aron Reply
Diversity of living thing
ISCONT
what is cell division
Aron Reply
Cell division is the process by which a single cell divides into two or more daughter cells. It is a fundamental process in all living organisms and is essential for growth, development, and reproduction. Cell division can occur through either mitosis or meiosis.
AI-Robot
What is life?
Allison Reply
life is defined as any system capable of performing functions such as eating, metabolizing,excreting,breathing,moving,Growing,reproducing,and responding to external stimuli.
Mohamed
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Source:  OpenStax, Mathematics grade 5. OpenStax CNX. Sep 23, 2009 Download for free at http://cnx.org/content/col10994/1.3
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