NUM 13-Jan-16Created by Mr. Lafferty Maths Dept. Decimal Numbers What is a decimal ? Decimal Scales ...

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21 Apr 202321 Apr 2023 Created by Mr. Lafferty Maths Dept.Created by Mr. Lafferty Maths Dept.

Decimal Decimal NumbersNumbers

What is a decimal ?

Decimal Scales

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Dividing by 10, 100, 1000

Multiplying by a single Digit

Rounding

Addition and Subtraction

Multiplying by 10, 100, 1000

Dividing by a single Digit

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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%

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21 Apr 202321 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 Decimals

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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

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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

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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

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Writing Decimals

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

(a) (b)

(c) (d)

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Now try Lifeskills Ex 1

Ch2 (page 9)

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Writing Decimals

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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

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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 how to read decimal scales.


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

Reading Scales

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21 Apr 202321 Apr 2023 Compiled by Mr. Lafferty Maths Dept.Compiled by Mr. Lafferty Maths Dept.ww

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Litres

1

2

0

How much liquid in the jug ?

going up 0.2 each time

0.8 litres

Decimal ScalesDecimal Scales

1 ÷ 5 = 0.2

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Litres

1

2

0

How much liquid in the jug ?

1.4 litres


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Litres

1

2

0

How much liquid in the jug ?( Careful different scale)


1.75 litres


1 ÷ 4 = 0.25

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Calculate the weight each arrow is pointing at?


grams

0 1g

2g

3g

4g5g

1.2g

2.8g

5.4g


1 ÷ 5 = 0.2

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grams

0.1

0.2

0.3

0.40.5

0.04g

0.36g

0.52g


0


0.1 ÷ 5 = 0.02

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Kilograms

0 2

4

6

810

0.8kg

7.2kg

10.4kg



2 ÷ 5 = 0.4

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Ch2 (page 10)

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Writing Decimals

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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.

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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 place

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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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RoundingRoundingRounding to Any Number of Decimal Places

When rounding to :

1 decimal place look at 2nd decimal figure

e.g. 2.46

e.g. 6.456

e.g. 3.7846

e.g. 13.1146

2 decimal place look at 3rd decimal figure3 decimal place look at 4th decimal figure4 decimal place look at 5th decimal figure

MNU 3-01a

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Example :

Rounded to 1 decimal place, the number is

4.3

4.26

4.262

4.2616

Rounded to 2 decimal place, the number isRounded to 3 decimal place, the number isRounded to 4 decimal place, the number is

MNU 3-01a

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Example : Use your calculator to find the answers to

62.73

Round your answers to 2 decimal places.

MNU 3-01a

134.59

4.29

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Ch2 (page 12)

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Writing Decimals

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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 Decimals

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Example : Calculate 7.8 + 0.92

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


8 7 2

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Example : Calculate 4 – 0.84

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


3 1 6

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Example : Find the value x cm and y cm


2.1cm3.91cm

x cmx cm y cm

y cm3.25cm

2.2cm

6 0 1 1 0 5

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Ch2 (page 14)

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Writing Decimals

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3. Calculate 712 - 6.7

4. Calculate the value of the missing angle.

23o

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

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


2. Show appropriate working.

Multiplication by a Single Digit

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

Example :Calculate 23.68 x 7


1 6 5 7 6

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6.52 x 2



1 3 0 4

95.05 x 5

4 7 5 2 5

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Ch2 (page 16)

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3. Calculate 72 - 58


57o

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

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


2. Show appropriate working.

Division by a Single Digit

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

Example : Calculate 17.16 ÷ 6


2 8 6

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6.37 ÷ 7


0 9 1

75.60 x 5

1 5 1 2


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Ch2 (page 18)

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1. 46 x 3


3.


35 ?=50 10

1 of 4907

40 o

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1.1. Understand the rules for Understand the rules for multiplying decimal numbers by 10, 100, 1000.

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

2.2. Be able solve problems Be able solve problems using rules.using rules.



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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

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

e.g. 1.023 x 100 = 102.3 point is moved 2 places to right


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

e.g. 34.5674 x 1000 = 34567.4 point is moved 3 place to right


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Example : Calculate the following

22.7 x 10 69.2 x 100 0.12 x 1000

= 227 = 6920 = 120


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Practice

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Ch2 (page 18)

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1. By rounding to 1 sig. fi g. estimate 28 x 76


3.


56 ?=80 10

1 of 2464

126 o

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1.1. Understand the rules for Understand the rules for dividing numbers by 10, 100, 1000

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

2.2. Be able solve problems Be able solve problems using rules.using rules.



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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


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

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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


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Example : Calculate the following

452.4 ÷ 10 67 ÷ 100 0.86 ÷ 1000

= 45.24 = 0.67 = 0.00086


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Practice


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Ch2 (page 18)

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NUM 13-Jan-16Created by Mr. Lafferty Maths Dept. Decimal Numbers What is a decimal ? Decimal Scales ...

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Transcript of NUM 13-Jan-16Created by Mr. Lafferty Maths Dept. Decimal Numbers What is a decimal ? Decimal Scales ...