Download Lesson 3 - Operations with Fractions

Operations
with
Fractions
By
Teacher Angelo
Addition and Subtraction of
Like Fractions
Examples:
Same denominator
1.) 2/7 + 3/7 = 5/7
2.) 8/15 + 2/15 = 10/15 or 2/3
3.) 7/11 - 2/11 = 5/11
4.) 6/17 - 2/17 = 4/17
Addition and Subtraction of
Unlike Fractions
different denominators
Examples on the board
Properties of Addition
1.) Commutative property of addition
Examples
1.) 2/3 + ½ = ½ + 2/3
2.) 3/9 + ¾ = ¾ + 3/9
Special Seatwork: (For 5 points)
Give 5 examples of commutative
property of addition.
2.) Associative property of addition
Examples
1.) (2/3 + ½ ) + ¾ = 2/3 + ( ½ + ¾ )
2.) (3/9 + ¾) + ½ = 3/9 + ( ¾ + ½)
Special Seatwork: (For 5 points)
Give 5 examples of Associative property
of addition.
Workbook
Exercise A
Number 1, 2, 3 and 4
on page 39 to 41
Multiplication and Division of
Fractions
Multiplication of fractions by
whole numbers
Workbook
Exercise B
Number 1, 2 and 3
on page 42
Multiplication with Fractions
Rule:
Multiply the numerators and
the denominators respectively
and then, simplify.
Example 1:
1 x 3 =1x3
2
4 2x4
=3
8
Example 2:
2 x 1 =2x1
3
4 3x4
= 2
12
=1
6
Board Work: More Examples
On Multiplication with
fractions
Workbook
Exercise B
Number 4
on page 43
Division with Fractions
Rule:
Find the reciprocal of the
divisor, multiply it to the
dividend then, simplify.
Example 1:
1 ÷ 3 =1 x4
2
4 2 3
=4
6
=2
3
Example 2:
3 ÷ 5 = 3 x 6
8
6
8 5
= 18
40
= 9
20
Board Work: More Examples
On Division with fractions
Workbook
Exercise B
Number 4 and 5
on page 43
Group Work:
Workbook
Exercise B
Number 6 and 7
on page 44
Solving Word Problems with Fractions
Example 1
Albert ate 3/8 of a cake baked by his mother.
His sister ate 1/8 of it. What fraction of the
cake did they both eat in total?
We Understand
Question: What fraction of the cake did
they both eat in total?
Given: Albert ate 3/8 of a cake and his
sister ate 1/8 of it.
We Plan
Key word : total
Operation: addition
We Solve
Number Sentence: 3/8 + 1/8 = _____
Working: 3/8 + 1/8 = 3 + 1
8
= 4
8
= 1
2
We Check
By commutative property of addition:
3/8 + 1/8 = 1/8 + 3/8
1=1+3
2
8
1= 4
2 8
1= 1
2 2
Answer: They both ate ½ part of the cake
in total.
Workbook
Exercise C
Letter B, C, D, E, F, G and H
on page 46 to 52.
Solving mixed operations with
fractions.
Example 1
Working on the board:
Example 2
Example 3
Practice: Write and solve the following
in your notebook.
Special Seatwork ( 3 points)
Answer: 2/5
Special Seatwork ( 3 points)
Answer: 12/121
Special Seatwork ( 3 points)
Answer: 1
Special Seatwork ( 3 points)
Answer: 1/2
Special Seatwork ( 3 points)
Answer: 7/10
Special Seatwork ( 3 points)
Answer: 1/2
Special Seatwork ( 3 points)
Answer: 2/7
Special Seatwork ( 3 points)
Answer: 8/21
Special Seatwork ( 3 points)
Answer: 19/60
Special Seatwork ( 3 points)
Answer: 2/3
Special Seatwork ( 3 points)
Answer: 5/84
Special Seatwork ( 3 points)
Answer: 3/28
Workbook
Exercise D
Number 1 and 2
on page 53.
Activity number 9
Solving mixed-operation word
problems with fraction
Example 1
Workbook
Exercise E
Letter A, B, C and D
Lesson 3 Test
+
Vocabulary and Spelling Test