1. Multiplying and Dividing Fractions
Our Lesson
Multiplying and Dividing Fractions

2. Warm up 4/5 +7/8 67/40 2/7 + 6/7 8/7 9/12 + 4/9 43/36 9/10- 6/10 3/10
4/5 +7/ /40
2/7 + 6/ /7
9/12 + 4/ /36
9/10- 6/ /10
5/8- 3/ /8
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3. Lets review what we have learned in the last lesson
Addition of Fractions
Addition means combining objects in two or
more sets
the objects must be of the same type, i.e. we
combine bundles with bundles and sticks with
sticks.
in fractions, we can only combine pieces of the
same size. In other words, the denominators
must be the same.
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4. Addition of Fractions Example 1 3 8 8 + With equal denominators
The answer is (1+3) 8
Which can be simplified to 1 2
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5. Addition of Fractions with different denominators
When the denominators are co-prime, we need to multiply the two denominators to get the common denominator
When the two denominators have a common factor we find the least common denominator by factoring
When one denominator is a multiple of the other denominator the multiple is the denominator
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6. Subtraction of Fractions
subtraction means taking objects away
the objects must be of the same type,
i.e. we can only take away apples from a group of apples
- in fractions, we can only take away pieces of the same size. In other words, the denominators must be the same
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7. Subtraction of Fractions
Example: - - = 8 12 =
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8. Multiplying fractions
Lets get Started
Multiplying fractions
To multiply two fractions
multiply the numerators
and
multiply the denominators
a c
b d ac bd
b,d = 0 x =
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9. Multiplication of mixed fractions
First convert the mixed fraction in to an improper fraction
Then multiply, numerator x numerator
and
denominator x denominator
Then again convert answer in to mixed number 19 1 12 1 6 2 4 38 = x
31 x 38
6 x 4 =
589 12 = = 49 5 x 9 3
Improper fraction
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10. Lets see some more Examples
2/9 x 5/ x
9 x = = 3 5 4 9
2) 3 x = x 7 36 45
18 x
5 x = = 26 =
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11. To divide fractions , multiply by its multiplicative inverse
Division of Fractions
To divide fractions , multiply by its multiplicative inverse
a c
b d
a d
b c ÷ = x
Where b, c and d = 0
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12. Steps for dividing fractions
1) Flip the second fraction over so that it would look like this
Numerator (N) Denominator
Denominator (D) Numerator
2) Now multiply the numerators and the denominators and put the product of the numerators over the product of the denominators
Numerator Denominator
Denominator Numerator x
2nd fraction
1st fraction
changed
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13. The number 0 has no reciprocals
Check this out
If the product of two numbers is 1 , they are the reciprocals of each other
The number 0 has no reciprocals
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14. Lets see some examples 1) 5/8 ÷ 7/6 5 6 30 8 7 56 = x = 4 3 4 8 36
1) 5/8 ÷ 7/ = x = = ÷ x =
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15. Division of mixed fractions
First convert the mixed fraction in to an improper fraction
Then multiply, Numerator x Denominator
Denominator x Numerator
Example: 3 4 4 9 ÷ 5 x = x 2 = =
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16. Your turn 3/7 x 3/9 9 /63 4/9 x 3/5 12/45 2/5 x 6/7 12/35
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17. Your turn
6) 10 1/3 ÷ 5 2/ /111
7) 8/11 ÷ 6/ /33
8) 4/7 ÷ 1/ /7
3 5/7 ÷ 4 3/ /28
21/9 ÷ ___ = /3
For Q.10 Do not use the reciprocals of the same fraction
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18. Break Time
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19. Click here to play a game
It's GAME TIME !!!!
Click here to play a game
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20. 1) In 1513, Juan Ponce de Leon discovered Florida
1) In 1513, Juan Ponce de Leon discovered Florida. His route from Puerto Rico to Florida measures about 2 ¼ inches on the map. If 1 inch represents 667miles, find the approximate length of the route.
1,500 ¾ miles
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21. Yes, there is enough turkey for 15 people
2) Nick is serving a 12 pound turkey at a dinner party. As a rule, you should allow about ¾ of a pound of meat per person. If he invited 15 people, will he have enough turkey? Use the equation ¾ p = 12 where p is the number of people.
Yes, there is enough turkey for 15 people
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22. 3) By law, the length of an official U. S
3) By law, the length of an official U.S. flag must be 1 9/10 times its width. If the width of a flag is 3 ½ feet, what is its length?
6 13/20 ft
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23. Multiplying fractions
Lets review what we learned in this lesson
Multiplying fractions
To multiply two fractions
multiply the numerators and
then multiply the denominators
a c
b d ac bd
b,d = 0 x =
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24. To divide fractions , multiply by its multiplicative inverse
Division of Fractions
To divide fractions , multiply by its multiplicative inverse
a c
b d
a d
b c ÷ = x
Where b, c and d = 0
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25. You had a Great lesson today!
Be sure to practice what you have learned today
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