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Glencoe Math: Course 1, Volume 1

GM

Glencoe Math: Course 1, Volume 1 View details

4. Percents Greater than 100% and Percents Less than 1%

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Exercise 17 Page 122

Practice makes perfect

We are given a table that shows the elements in the human body. We want to write the percent of magnesium found in the human body as a decimal.

Elements in the Human Body
Element	Percent
Magnesium	0.05
Potassium	0.35
Sodium	0.15
Sulfur	0.25

We will rewrite 0.05 % as a decimal. To write a percent as a decimal, we ignore the percent symbol and move the decimal point two places to the left.

We found that the percent of magnesium in the human body written as a decimal is equal to 0.0005.

Now we want to find which element makes up 1400 of the human body. Let's look at our table again.

Elements in the Human Body
Element	Percent
Magnesium	0.05
Potassium	0.35
Sodium	0.15
Sulfur	0.25

We will rewrite each percent as a fraction in simplest form. Let's start with 0.05 %. To write a percent as a fraction, we write the number part as the numerator and 100 as the denominator. 0.05 % = 0.05/100 Let's simplify this fraction.

0.05/100

a/b=a * 100/b * 100

5/10 000

a/b=.a /5./.b /5.

5÷ 5/10 000÷ 5

Calculate quotient

1/2000

Next, let's rewrite 0.35 %. In this fraction, 0.35 is the numerator and 100 is the denominator. 0.35 % = 0.35/100 Let's simplify this fraction.

0.35/100

a/b=a * 100/b * 100

35/10 000

a/b=.a /5./.b /5.

35÷ 5/10 000÷ 5

Calculate quotient

7/2000

Now we will write 0.15 % as a fraction. 0.15 % = 0.15/100 Let's simplify.

0.15/100

a/b=a * 100/b * 100

15/10 000

a/b=.a /5./.b /5.

15÷ 5/10 000÷ 5

Calculate quotient

3/2000

Finally, let's write 0.25 as a fraction. 0.25 % = 0.25/100 Let's expand the fraction by 100 and simplify.

0.25/100

a/b=a * 100/b * 100

25/10 000

a/b=.a /25./.b /25.

25÷ 25/10 000÷ 25

Calculate quotient

1/400

Let's write our results in the table.

Elements in the Human Body
Element	Percent	Fraction
Magnesium	0.05	1/2000
Potassium	0.35	7/2000
Sodium	0.15	3/2000
Sulfur	0.25	1/400

Sulfur makes up 1400 of the human body.

Subchapter links

Guided Practice p.120

Independent Practice p.121-122

H.O.T. Problems p.122

Standardized Test Practice p.122-124

Extra Practice p.123

Common Core Review p.124