Topic 3 (Decimal)-Y4 09.ppt

8/14/2019 Topic 3 (Decimal)-Y4 09.ppt

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Murugiah Velayutham/TCG 2

DECIMALSWhat is decimal?It means “based on 10”Latin decima: a tenth part Decimal number – Any number written in a

base-ten system can be called a decimalnumber.

123- is a decimal ( since each digit worth tentimes as much as the one next to it)

1.23- is a decimal (with a decimal point in it)




DECIMALS1. We must provide opportunities for

our children to learn and understanddecimals meaningfully.

2. We use physical materials and otherrepresentatives to help childrenunderstand the concept of decimals

(a) Area models (fraction circles)(b) Linear models (fraction strips)(c) Discrete models (counters)




DECIMALS3. It would be useful to show students

these representations to reaffirmtheir understanding about decimals

4. It is important for us to have anoverview of the mathematical skillsinvolved in changing fractions andmixed numbers to decimals and viceversa.




Guidelines to read and write adecimal number:

1. Mentally align the whole numbers in the placevalues chart and the decimal numbers in thedecimal place chart.

2. Read the whole number.3. Use the decimal point and read the decimal

place value as you read the whole number.

4. End by reading the last decimal place valuewhere the numbers end.




Reading Decimal numbers

• Read the following Decimal numbers:• 1.12 : one and twelve hundredths• 14.345 : Fourteen and three hundred

and forty five thousandths• 1.3?• 0.15??• 0.105???




Converting Fraction toDecimal

Example : Write as a decimal. Solution:1. Write the numerator 18

2. Count how many zeros are thereat the denominator 3

3. Move the decimal point three placesfrom right to the left. Attach zeroson the left end of the decimal point 0.018

1000

18




Converting Fraction toDecimal

Fraction to Decimal Follow the following steps:1. Place the decimal point after the number of

the numerator.2. Attach the zeros as needed after the

decimal point3. Divide the numerator by denominator using

long division




Fractions to Decimals Example 1: Convert to decimal number.Solution:

Place a decimal after six.

Attach zeros as needed.Divide as usual.

8

6

75.0

0

4040

6.5

00.68




Converting Decimal toFraction

Decimals to FractionsFollow the following steps:1. Write the numerator as whole number.2. Write the denominator as power of tens with

number of zero depends on how many placesafter the decimal point.

3. Reduce the fraction.




Decimals to FractionsExample 1: Convert 0.5 to fraction.Solution:

The numerator should bethe whole number, 5The denominator 10 (onezero)

Write the fractionSimplify the fraction

2

1

10

5

5.0




Decimals to Fractions

Example 2: Convert 0.085 to fractions.Solution:The numerator should be thewhole number, 85

The denominator 1000(three zeros)Write the fraction

Reduce the fraction

200

17

1000

85085.0




Converting Mixed Numbersto fractions Vice Versa

Mixed Numbers to FractionsFollow the following steps:

1. Write the mixed number as whole numberand decimal number.2. Convert decimal number to fraction.

3. Convert fraction to mixed number fractions.




Mixed Numbers to FractionsExample : Convert 17.32 to mixed number fractions1. 17.32 = 17 and 0.32 Write in whole numbers

and decimal numbers

2. 0.32 = Convert decimal numbers tofraction and reduce thefraction

3. Write the fractions

25

8

100

32

25

817




Mixed Numbers to decimals

Example : Convert to decimal number

1. = 13 and Write in whole numbersand fractions

2. Convert the fraction todecimal numbers by longdivision

3. Write the decimal numbers

4

313

4

313

4

3

0

02

02

82

75.0

00.34

75.134

313




Addition & Subtraction ofDecimals

Addition of Two Decimal NumbersSteps to follow for adding two decimals: 1. Arrange the decimal numbers so that the decimal

points are in vertical line

2. Add the numbers of the same digit place from rightto left.3. Place the answers in the same place.Example: 7.93 + 12.75

12 23 . 7 5+ 7 . 9 3

2 0 . 6 8




Subtraction of Two Decimal NumbersSteps to follow for subtracting two

decimals: 1. Arrange the decimal numbers so that the

decimal points are in vertical line

2. Subtract each number from right to left.3. Place the answers in the same place.Example: Subtract 12.75 from 17. 93.

1 7 . 9 8 313 -1 2 . 7 5

5 . 1 8




Addition & Subtraction of ThreeDecimal Numbers

Example 1: Add 65.00 + 42.56 + 55.1276 5 . 0 0

4 2 . 5 6+ 5 5 . 1 2

1 6 2 . 6 8Example 2 : Subtract 52.97 – 17.33 – 10.58

54 212 . 9 7 3 5 . 6 5 414

- 1 7 . 3 3 - 1 0 . 5 83 5 . 6 4 2 5 . 0 6




Multiplication & Division ofDecimals

Multiplication of Decimal NumbersSteps to follow for multiplication of decimals: 1. Place the decimal above the other so that they are

lined up vertically.

2. Disregard the decimal points and multiply thenumbers.3. Count the total number of digits to the right of the

decimal point for both decimal numbers.

4. Place the decimal point in the product by moving thedecimal point from right to left of the digitsaccording to number of digits count in Step 3.




Multiplication of Decimal Numbers

Example 1: Multiply 1.639 x 0.573 1 44 2 6

1 . 6 3 9 3 decimal placesx 0 . 5 7 2 decimal places1 1 4 7 3

+ 8 1 9 5 00. 9 3 4 2 3 5 decimal places




Division of Decimal NumbersSteps to follow for division of decimals: 1. Write the division using a longdivision (√). 2. Insert the decimal point above the decimal in

the dividend.3. Proceed with the division of whole number




Division of Decimal NumbersExample 1: Divide the following: 16.15 ÷ 2.4

1. Move the decimal point in dividendand divisor so that the divisor isa whole number.

2. Insert the decimal point above

the decimal in the dividend.3. Proceed with the division

.

15.164.2

7.6

7

168

175

144

5.16124




Multiplication of Decimals in StandardWritten MethodExample 1: 19.15 x 100Move decimal point to two places

19.15 x 100 = 1915

Example 2: 195.17 x 1000

Move decimal point to three places195.17 x 1000 = 195170




Division of Decimals in StandardWritten MethodExample 1: 19.15 ÷ 100

Move decimal point two places to the left19.15 ÷ 100 = 0.1915

Example 2: 195.17 ÷ 1000Move decimal point to three places

195.17 ÷ 1000 = 0.19517

Topic 3 (Decimal)-Y4 09.ppt

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