Fraction Rules
When we multiply fractions we multiply...
straight across!
2/3 * 4/5
8/15
1 1/2 -: 5/7
21/10 or 2 1/10
A grocery store sells tangerines in 2/5 kg bags. A customer bought 4 kg of tangerines for a school party. How many bags did he buy?
He bought 10 bags.
All fractions are also what type of problem?
division problems
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
5/6 * 1 1/3
10/9 or 1 1/9
There is gallon 1/3 of water in a 3-gallon container. What fraction of the container is filled?
The container is filled 1/9th of the way.
In a division equation, if the divisor is smaller than the dividend then the quotient will be _______ than 1.
greater
3 word phrase to help us with dividing fractions.
Keep - Change - Flip
4 * 7/8
7/2 or 3 1/2
6 3/4 -: 1/8
54
2/5 kilogram of soil fills 1/3 of a container. Can 1 kilogram of soil fit in the container?
Explain or show your reasoning.
No, 1 kg cannot fit into the container. If 2/5 is 1/3, 4/5 is 2/3, so 6/5 is 3/3 (the entire container).
OR
No, because 2/5 divided by 1/3 is 6/5 (or 1 1/5), which is more than 1 kg of soil.
How do we convert a mixed number into a fraction?
Use the "C" method. Multiply the denominator with the whole number and add the numerator.
What is the reciprocal of
11/8
8/11
5/12 * 9
15/4 or 3 3/4
1 1/3 * 2 1/8
17/6 or 2 5/6
2. A zookeeper is 6 1/4 feet tall. A young giraffe in his care is 9 3/8 feet tall.
a. How many times as tall as the zookeeper is the giraffe?
b. What fraction of the giraffe’s height is the zookeeper’s height?
a. The giraffe is 1 1/2 times taller than the zookeeper.
b. The zookeeper is 2/3 the height of the giraffe.
What is the first rule in dividing fractions?
Keep fraction the same.
What should you do first to mixed numbers when multiplying or dividing fractions?
Convert them to fractions greater than 1.
Change them to fractions greater than 1.
Make them fractions greater than 1.
2/9 * 3/8
1/12
2 2/3 -: 5 1/4
32/63
2. A rectangular prism measures 2 2/5 inches by 3 1/2 inches by 2 inch.
a. Priya said, “It takes more cubes with edge length 2/5 inch than cubes with edge length 1/5 inch to pack the prism.” Do you agree with Priya? Explain or show your reasoning.
b. How many cubes with edge length 1/5 inch fit in the prism? Show your reasoning.
a. No, it would actually take fewer 2/5 cubes because they are bigger and have a ;arger volume. Because they take up more space inside an object, you need fewer of them to fill the space.
b. It would take 1,920 cubes because 12 x 16 x 10 = 1,920.
How do we convert a fraction greater than 1 into a mixed number?
Make as many whole groups as you can and what is left if the numerator over the SAME denominator.