REVIEW: Dividing Fractions
Dividing is the same as multiplying by the reciprocal. So, to divide fractions, you have to:
1. Keep the first fraction.
2. Change the division symbol to ________.
3. Flip the second fraction to the ________.
multiplication
reciprocal
Make an equivalent ratio by filling in the blank.
1:8 = 5: _____
1:8 = 5:40
We are scaling up by 5!
Are these ratios equivalent?
14 pages : 2 days
35 pages : 7 days
We are looking for a common denominator.
14:2 = 7:1
35:7 = 5:1
Not equivalent!
1/2 \div 1/4 =
1/2 \div 1/4 = 1/2 \times 4/1 = 4/2 = 2
Make an equivalent ratio by filling in the blank.
12:15 = 4:_____
12:15 = 4:5
We are scaling down by 3!
Make these ratios equivalent:
1 old boat for every 6 new boats
4 old boats for every _____
24
13/15 \div 13/15 =
1
Any number divided by itself is 1.
Make an equivalent ratio by filling in the blank.
8:9 = ____ : 108
8:9 = 96:108
We are scaling up by 12!
In Mr. Murphy's closet, his ratio of shirts to pants to shorts is 4:3:5. He has 12 shirts, _______ pants and ______ shorts.
we are scaling up by 3.
So he has 3 x 3 = 9 pants
and 5 x 3 = 15 shorts
Make sure to reduce your answer:
7/10 \div 8/10 =
7/10 \div 8/10 = 7/10 \times 10/8 = 70/80 = 7/8
Make equivalent ratios by filling in the blank.
8:64 = ____:16 = 1:_____
8:64 = 2:16 = 1:8
In a recipe for cake, the ratio of sugar to flour is 2:3. You are baking cake for the whole middle school, so you need 42 cups of flour. How much sugar do you need?
(sugar)/(flour) = 2/3 = 28/42
3 \times 14 = 42 cups of flour
2 \times 14 = 28 cups of sugar
Write your answer as a mixed number.
4/5 \div 5/8 =
4/5 \div 5/8 = 4/5 \times 8/5 = 32/25 = 1 7/25
Make equivalent ratios by filling in the blanks.
72:8 = _____ : 1 = 27 : ______
72:8 = 9:1 = 27:3
4/10 = ____ /35
We need to scale up by 3.5 because 10 x 3.5 = 35.
So 4 x 3.5 = 14.
We could also scale 4/10 down to 2/5 and then multiply up by 7. 4/10 = 2/5 = ____ /35.