25-Aug-14Created by Mr. Lafferty Maths Dept. Working with Decimals Decimal Scales Decimal Numbers ...

11 Apr 202311 Apr 2023 Created by Mr. Lafferty Maths Dept.Created by Mr. Lafferty Maths Dept.

Working with Decimals

Decimal Scales

Decimal Decimal NumbersNumbers

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Multiplying and Dividing by 10, 100, 1000

Multiplying and Dividing by a single Digit

Rounding to 1 Decimal Place

Addition and Subtraction

MNU 2-03b MNU 2-04a


Starter QuestionsStarter Questionsw

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1. Find the missing value

2. Calculate of 6000

3. What is the next three numbers in the sequence 9, 15, 21, 27, ...., ...., .... 4. Round 72 to the nearest 10

3 ?=4 20

20%

MNU 2-03b MNU 2-04a

11 Apr 202311 Apr 2023 Created by Mr. Lafferty Maths Dept.Created by Mr. Lafferty Maths Dept.ww

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1.1. Understand what a decimal Understand what a decimal number is.number is.

1. We are learning what a decimal number is. Write down the decimal number represented by a fraction diagram.


2.2. Write down the decimal Write down the decimal number represented by a number represented by a fraction diagram.fraction diagram.

Writing DecimalsMNU 2-03b MNU 2-04a


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When you take a When you take a single unitsingle unit and divide it and divide it into 10 bitsinto 10 bits, , what we then have are what we then have are

decimal fractionsdecimal fractions of a whole number of a whole number

Writing Decimals

Imagine, 1 bar of chocolate as our UNIT of measure.

1 (of 1 bar)

10

or 0.1

1

0.110 1. 0

0.1 0.40.2 0.3 0.5

0.6 0.90.7 0.8 1.0

means ten

MNU 2-03b MNU 2-04a


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Writing Decimals

Example : Write down the decimal number represented by the shaded area.

(a)

(b)

0.3

3 "which means 3 tenths = "

10

0.5

5 1 "which means 5 tenths = = "

10 2

MNU 2-03b MNU 2-04a


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Writing Decimals

Example : Write down the decimal number represented by the diagram.

(a) (b)

(c) (d)

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We can take one bit of the chocolate bar We can take one bit of the chocolate bar and split it into 10and split it into 10

Writing Decimals

0.10.01

1st Decimal place

2nd Decimal place

MNU 2-03b MNU 2-04a


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Writing Decimals

Example : Write down the decimal number represented by the diagram.

(a) (b)

(c) (d)

MNU 2-03b MNU 2-04a


Now try Exercise 1

Ch2 (page 25)

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Writing DecimalsMNU 2-03b MNU 2-04a



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2. Calculate 30% of 900

3. Find the area of the rectangle

6cm in length by 4 cm wide.

4. Name the shape.

3cm

MNU 2-03b MNU 2-04a


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1.1. Understand the steps to Understand the steps to work out any decimal scale work out any decimal scale to 2 decimal places.to 2 decimal places.

1 We are learning the steps to read decimal scales.


2.2. Solve problems by working Solve problems by working out scales. out scales.

Reading ScalesMNU 2-03b MNU 2-04a


You must work out what number goes next to each markon the scale.

Step 1: Count the number of steps between numbers.

In this case it takes 10 steps to get from 0.0 to 1.0cm.

Step 2: Do the division

“ the difference between numbers”by the step number

1.0 ÷ 10 = 0.1cm

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0.0 1.0cm 2.0cm

0.10.2

0.30.4

0.50.6

0.70.8

0.9

1.11.2

1.31.4

1.51.6

1.71.8

1.9




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Find the values of the arrows

8.3 8.8 9.5 9.8

8 9cm 10cm


In this case it takes 10 steps to get from 8 to 9cm.



1 ÷ 10 = 0.1cm9-8=1

10




You must work out what number goes next to each markon the scale.


In this case it takes 10 steps to get from 3.00cm to 3.10cm.



0.1 ÷ 10 = 0.01cm

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3.00cm 3.10cm 3.20cm

3.013.02

3.033.04

3.053.06

3.073.08

3.09

3.113.12

3.133.14

3.153.16

3.173.18

3.19


Reading Harder ScalesMNU 2-03b MNU 2-04a



In this case it takes 10 steps to get from 12.00cm to 12.10cm.



0.1 ÷ 10 = 0.01cm

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12.00cm 12.10cm 12.20cm


Reading Harder Scales

12.03 12.08 12.14 12.19

MNU 2-03b MNU 2-04a


Now try Exercise 2Ch12 (page 28)

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o3. I f I am f acing North and turn 90 clockwise, which direction am I f acing

4. How many lines of symmetry has the shape.

MNU 2-03b MNU 2-04a


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1. We are learning how to round to 1 decimal place.


1.1. Remember steps to Remember steps to round round to 1 decimal place.to 1 decimal place.

Rounding to 1 decimal placeMNU 2-03b MNU 2-04a


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8.2cm 8.3cm 8.4cm


8.24 8.28 8.35

Rounding to 1 decimal place

Find the values of the arrows.

Is 8.24 nearer to 8.2 or 8.3 ? 8.2Is 8.28 nearer to 8.2 or 8.3 ? 8.3Is 8.35 nearer to 8.2 or 8.3 ? Neither

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Rounding to 1 decimal place

If the 2nd decimal place is 0,1,2,3,4 - leave 1st decimal place as it is

Example : Round the numbers to 1 decimal place

(a) 9.04 (b) 18.08 (c) 24.25

(d) 12.73 (e) 102.09 (f) 2636.55

If the 2nd decimal place is 5,6,7,8,9 - add 1 to 1st decimal place

The rules for rounding to 1 decimal place are:

MNU 2-03b MNU 2-04a



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Rounding to 1 decimal placeMNU 2-03b MNU 2-04a



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1. 13 x 7

2. Calculate 23 x 10

3.

4. Find the missing number

3 of 804

1, 1, 2, 3, 5, 8, ...., ...., ....

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1. We are learning how to add and subtract decimal numbers.

1. Understand that you must keep the decimal point lined up when adding and subtracting decimal numbers.


2. Show all working.

Add and Subtract DecimalsMNU 2-03b MNU 2-04a


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Example 1 : Calculate 7.8 + 0.92

When you add or subtract decimal numbers, it is important to line-up the decimal points.

Add and Subtract Decimals

7.80

+0.928 .721

MNU 2-03b MNU 2-04a


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Example 1 : Calculate 4 – 0.84

When you add or subtract decimal numbers, it is important to line-up the decimal points.


3 9 1 4 . 0 0

- 0

. 8 43

. 1 6

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Example 1 : Find the value x cm and y cm


3. 25

-

2.201. 05

2.1cm3.91cm

x cm

2. 10

+ 3.916 .011

x cm y cm

y cm3.25cm

2.2cm

MNU 2-03b MNU 2-04a



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Add and Subtract DecimalsMNU 2-03b MNU 2-04a



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1. 46 x 3

2. Find the missing value

3.

4. Calculate the value of the missing angle.

35 ?=50 10

1 of 4907

40 o

MNU 2-03b MNU 2-04a


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1.1. Understand the simple rules Understand the simple rules to multiply and divide to multiply and divide decimal numbers.decimal numbers.

1 We are learning how to multiply and divide decimal numbers by 10, 100, 1000.

2.2. Be able do calculations.Be able do calculations.


Multiplying & Dividing by 10, 100, 1000MNU 2-03b MNU 2-04a


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To multiply a decimal number by 10, Simply move point 1 place to the right:

e.g. 2.55 x 10 = 25.5 point is moved 1 place to right

Multiplying by 10, 100, 1000

To multiply a decimal number by 100, Simply move point 2 places to the right:

e.g. 1.02 x 100 = 102.0 point is moved 2 places to right

MNU 2-03b MNU 2-04a


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To multiply a decimal number by 1000, Simply move point 3 places to the right:

e.g. 34.567 x 1000 = 34 567 point is moved 1 place to right

Multiplying by 10, 100, 1000MNU 2-03b MNU 2-04a


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Example : Multiply 1.8574 by 10, 100, 1000

10 x 1.8574 =

100 x 1.8574 =

1000 x 1.8574 =

18.574

185.74

1857.4

Multiplying by 10, 100, 1000MNU 2-03b MNU 2-04a


Now try Ex 5First Column in each

Question ONLYCh2 (page 35)

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Multiplying & Dividing y 10, 100, 1000MNU 2-03b MNU 2-04a


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To divide a decimal number by 10, Simply move point 1 place to the left:

e.g. 89 ÷ 10 = 8.9 point is moved 1 place to left

Dividing by 10, 100, 1000

To divide a decimal number by 100, Simply move point 2 places to the left:

e.g. 199 ÷ 100 = 1.99 point is moved 2 places to left

MNU 2-03b MNU 2-04a


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To divide a decimal number by 1000, Simply move point 3 places to the left:

e.g. 35 837 ÷ 1000 = 35.837 point is moved 3 places to the left

Dividing by 10, 100, 1000MNU 2-03b MNU 2-04a


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Example : Divide 45 024 by 10, 100, 1000

45 024 ÷ 10 =

45 024 ÷ 100 =

45 024 ÷ 1000 =

4502.4

450.24

45.024

Dividing by 10, 100, 1000MNU 2-03b MNU 2-04a


Now try Ex 6First Column in each

Question ONLYCh2 (page 35)

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Multiplying & Dividing y 10, 100, 1000MNU 2-03b MNU 2-04a



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3. Calculate 72 - 58

4. Calculate the value of the missing angle.

57o

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1. We are learning how to multiply and divide a decimal number by a single Digit.

1. Understand how to multiply and divide a decimal number by a single Digit.


2. Show appropriate working.

Multiplication & Division by a Single DigitMNU 2-03b MNU 2-04a


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When multiplying by a single digit the decimal point always stays in line.

Example : Calculate 23.68 x 7

Multiplication & Division by a Single Digit

2 4 5

23.68

x 7165 .76

MNU 2-03b MNU 2-04a


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When dividing by a single digit the decimal point always stays in line.

Example : Calculate 17.16 ÷ 6

Multiplication & Division by a Single Digit

1 5 3

2 . 8 6 6 17. 16

MNU 2-03b MNU 2-04a


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3.5 x 6 18.43 x 4 76.97 x 6

6.52 ÷ 2 95.05 ÷ 5 204.84 ÷ 6




Now try Ex 7 & 8Ch2 (page 37)

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25-Aug-14Created by Mr. Lafferty Maths Dept. Working with Decimals Decimal Scales Decimal Numbers ...

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Transcript of 25-Aug-14Created by Mr. Lafferty Maths Dept. Working with Decimals Decimal Scales Decimal Numbers ...