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Math Journal 8-18
I you deposit $255 into an account that earns 4.2%, compounded twice a year, how much money will you have in your account after 3 years? !!
UNIT 1 DAY 6: APPLICATIONS WITH FRACTIONS
Essential Questions: How are fractions useful in real life situations? What is necessary to
add or subtract fractions? How is this different from multiplying or dividing fractions?
Reciprocal: two numbers are reciprocals if their product is 1.
Numerator: the number ABOVE the division line in a fraction. Shows how many parts of the denominator are taken.
Denominator: the number BELOW the division line in a fraction. Shows the total number of “pieces” that make up a fraction.
Vocabulary
Adding/Subtracting Fractions
You must get a common denominator in order to add or subtract fractions!
This does not apply when we are multiplying or dividing fractions.
Example 1In the state of Arizona you need 22 credits to graduate
high school. At the end of your sophomore year, you
have half of your credits completed. Each year you will
earn credits. How many total credits will you
have at the end of junior year?
6
22
Get a common
denominator
11 •11 •
+ 6
22
1 2
+ 6
22
11 22
17
22
=
You will have 17 credits out of the 22 total that you need at
the end of the semester.
Example 2A recipe needs teaspoon of black pepper and
teaspoon red pepper. How much more black pepper
is needed than red pepper?
Get a common
denominator
2 •
2 •-
18
3 4
- 1 8
6
8
5
8
=
You need 5/8 teaspoon more black pepper than red pepper.
Multiplying FractionsLine up the top of a fraction with the top of the other fraction.
Cancel out common factors.
Multiply across.
You own your own lawn cutting business and
charge $80 for every acre of grass cut. How
much would you charge for a yard that is
acre?
Example 3
= =20
1
You would charge $20 to cut a yard that is 1/4 acre.
14
Dividing FractionsLine up the top of a fraction with the top of the other fraction just like before.
Flip the second fraction to its reciprocal and change from division to multiplication.
Cancel out common factors.
Multiply across.
Original Number Reciprocal4/5 5/43/4 4/3
45/83 83/452 1/2
24 1/24
You have of a pie that you want to split up between 3
people. How much will each person get if the pie is split
up evenly?
Multiply by the reciprocal!
Example 4
= =
Each person gets 1/5 of the pie.
Fractions Games
http://www.math-play.com/Multiplying-Fractions-Millionaire/Multiplying-Fractions-Millionaire.html
http://www.math-play.com/math-basketball-dividing-fractions-game/math-basketball-dividing-fractions-game.html