Fraction Rules
What step is used to simplify fractions when multiplying or dividing?
Divide by a common factor
2/3 * 4/5
8/15
4 1/2 ÷ 2 4/5
1 17/28
What is the reciprocal of
11/8
8/11
Wire that is 10 1/2 inches long has to be cut into 7 equal pieces. What size are the pieces?
1 1/2 inches
How do we change a whole number into a fraction?
Put a 1 in the denominator, or put it over 1.
3/5 * 7/8
21/40
3 2/5 * 1/7
1/2
1/8 -: 3
1/24
There was 5/8 of a pie left. Daniel ate 1/4 of the left over pie. How much pie did he have?
5/32 of the pie
Do we use reciprocals when multiplying OR dividing fractions?
Dividing Fractions
2 x 2/68
1/17
1 1/4 ÷ 4 7/8
10/39
6 -: 1/8
48
A baker is making 18 pounds of dough. Each croissant needs 1/8 of a ound of dough, how many croissants can he make?
When multiplying mixed numbers, what do you have to do first?
Make them into Improper Fractions
5/12 * 9
15/4 or 3 3/4
2 1/3 * 5 1/4
12 1/4
1/2 -: 5
1/10
A pancake mix can make 12 pancakes per batch. Kathy is making 3 batches of pancakes. If each batch needs 7/12 cups of milks, how much milk does she need in total?
1 3/4 cups of milk
Why do we use a reciprocal?
Division of fractions is set up as a complex fraction, we need to get the denominator to one and whatever we do to the bottom, we have to do to the top
2/9 * 3/8
1/12
6 1/3 ÷ 3 1/2
1 17/21
1/12 -: 3
1/36
If a teach wants to give out 3/7 a slice of cake and the teacher has 9 slices left, how many students is she able to give cake to?
21 students