Bell work:

Use Prime Factorization to reduce 20/39

Answer:

2 x 2 x 5 = 5/9

2 x 2 x 3 x 3

S

Lesson 11Percents

In lesson 10 we compared fractions with common denominators by rewriting them. One way to express rational numbers with common denominators is as percents. The word percent means per hundred. The denominator 100 is indicated by the word percent or by the symbol %. One hundred percent equals one whole.

We could say that 50% is also 50/100 which reduces to ½. 5% means 5/100 which equals 1/20.

Write each percent as a reduced fraction.

1% 10% 100%

Answer:

1% = 1/100

10% = 1/10

100% = 1

One way to write a fraction as a percent is to find an equivalent fraction with a denominator of 100.

¼ = 25/100 = 25%

Write each fraction as a percent.

¾ 3/5 3/10

Answer:

¾ = 75/100 = 75%

3/5 = 60/100 = 60%

3/10 = 30/100 = 30%

Another way to convert a fraction to a percent is to multiply the fraction by 100%. This method applies the Identity Property of Multiplication since 100% is equal to 1.

For example, to convert 2/3 to a percent we can multiply 2/3 by 100% or 100%/1.

2/3 x 100%/1 = 200%/3

We complete the process by dividing 200% by 3 and writing any remainder as a fraction.

200%/3 = 66 2/3%

Write each fraction as a percent.

1/3 5/6 3/8

Answer:

1/3 = 100%/3 = 33 1/3%

5/6 = 500%/6 = 83 1/3%

3/8 = 300%/8 = 37 ½%

To write a percent as a fraction we replace the percent sign with a denominator of 100 and reduce if possible. If the percent is a mixed number, we rewrite it as an improper fraction before multiplying the denominator by 100 to remove the percent symbol.

Write each percent as a reduced fraction.

4% 40% 33 1/3%

Answer:

4% = 4/100 = 1/25

40% = 40/100 = 2/5

33 1/3% = 100%/3 = 100/300 = 1/3

Fractional part problems are often expressed as percents. To perform calculations with percents we first convert the percent to a fraction or decimal.

Example:

Forty percent of the 30 students rode the bus. How many of the students rode the bus?

Answer:

40% = 40/100 = 2/5

2/5 of 30 = 12

12 students rode the bus.

Example:

A quart is what percent of a gallon?

Answer:

4 quarts equal a gallon so a quart is ¼ of a gallon.

¼ = 25/100 = 25%

A quart is 25% of a gallon.

HW: Lesson 11 #1-30

Due Tomorrow