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

Summary

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?

Use 1 minute to write 2 sentences answering the essential questions.