• Before the bell rings... – Copy the weekly planner. – Have your covered textbook with you. 1. Put these in order for least to greatest. ¾ 2/3 5/8 5/7 2. Anna saw 171 fish during her 38- minute drive. At this rate, how many did she see in the first two minutes?
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• Before the bell rings...– Copy the weekly planner.– Have your covered textbook with you.
1. Put these in order for least to greatest. ¾ 2/3 5/8 5/7
2. Anna saw 171 fish during her 38-minute drive. At this rate, how many did she see in the first two minutes?
• Before the bell rings...– Copy the weekly planner.– Have your covered textbook with you.
1. Put these in order for least to greatest. ¾ 2/3 5/8 5/7
2. Anna saw 171 fish during her 38-minute drive. At this rate, how many did she see in the first two minutes?
5/8, 2/3, 5/7, 3/4
9 fish
Fractions
Adding and Subtracting
Essential Questions
1. What is the value of studying fractions?
2. What is the relationship between good number sense and working with fractions?
Rule for +, -
• Must have or get
COMMON DENOMINATORS
Add or subtract only the numerators, keeping the same denominator.
Simplify fraction into lowest terms
3
52
3
1)Find the LCM
2)Find the new numerators
3)Add the numerators
4)Simplify the fraction
15
10
15
19
15
41
15
9
• Subtract
4
52
7
1.Find the LCM2.Find the new numerators3.Subtract the numerators4.Simplify the fraction
35
28
35
10
35
18
Try these examples
2 37 5
3 4
39 2
5
12
95
12
87
=
= =12
1712 =
12
513
5
32
5
58 =
5
26
More examples
24
96
36
82
43
24
164
24
335
24
164
24
171
EXAMPLE 1 Adding and Subtracting Fractions
a. 78 + – 2
5 =3540
– 1640+ Rewrite fractions using LCD of 40.
=35 +( – 16)
40Write sum over LCD.
1940= Evaluate numerator.
b. 310
56
– = 930
2530
– Rewrite fractions using LCD of 30.
=9 – 25
30Write difference over LCD.
=– 1630
Evaluate numerator.
815
–= Simplify.
GUIDED PRACTICE for Example 1
Find the sum or difference. Then simplify if possible.2. 3
49
10– = 30
403640
– Rewrite fractions using LCD of 40.
=30 – 36
40Write difference over LCD.
– 640= Evaluate numerator.– 3
20=3
20
GUIDED PRACTICE for Example 1
Find the sum or difference. Then simplify if possible.3. 5
12– 79
+ = 45108
– 84108
+ Rewrite fractions using LCD of 108.
=45 – 84
108Write sum over LCD.
– 39108= Evaluate numerator.
13
36
1336=–
GUIDED PRACTICE for Example 1
Find the sum or difference. Then simplify if possible.5. 1
61115
– = 1590
6690
– Rewrite fractions using LCD of 90.
=15 – 66
90Write difference over LCD.
– 5190= Evaluate numerator.
– 1730= Simplify.
Homework
• Page 240 #1-13, 36-39
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