Applications of Percent

Grade 8: The Learning Equation Math

11.04 Applications of Percent

Refresher pp 7-8

The student will:

represent and apply fractional percents and percents greater than 100 in fraction or decimal form, and vice versa.

Percent Review You can model percent with a 100 square grid. Click on the individual pieces to add/subract pieces!! Remember a percent (%) can be written as fraction with a denominator of 100. Estimating Percent - visual and interactive
Percent	123 : 100 =123% 132/100 =132%	a ratio whose second term is 100. Percent means "parts per hundred". We use the symbol /100 or % for percent.
Converting Fractions to Percent	7/4 =175/100 =175% 7/5 =140/100 =140% 23/10 =230/100 =230% 59/25 =236/100 =236%	use equivalent fractions, if the denominator is a factor of 100. Algebra.help -- Fraction Simplifier
Converting Percent to Fractions	275% = 275/100 = 3/4 40% = 40/100 = 2/5 30% = 30/100 = 3/10 45% = 45/100 = 9/25	Change percent to a fraction with a denominatorof 100. Reduce to lowest terms. Quia - Matching - Percent - Fraction Match
Converting Fractions to Decimals	5/3 = 1.666... 15/9 = 1.555...	divide the numerator by the denominator if the denominator of the fraction is not a factor of 100. Converting Fractions to Decimals Algebra.help -- Fraction Simplifier Scientific Calculator
Converting Decimals to Fractions	0.84 = 84/100 = 21/25 1.43 = 1 43/100	Make sure there is at least two decimal places. Move the decimal to the end of the hundredth digit and then place this number over 100. Reduce to lowest terms. If there are more than two decimal places, then move the decimal to the end of the last digit, then place the number over the following denominators: 3 decimal places --> /1000 4 decimal places --> /10 000 Converting Decimals to Fractions Quia - Matching - Fraction Decimal Conversion
Converting Decimals to Fractions	0.333... = 3/9 0.666... = 6/9 = 2/3 1.555... = 1 5/9	For this course, the limit is single-digit nonterminating decimals. The denominator for these fractions is 9. Reduce to lowest terms. Quia - Concentration - Fraction Decimal Conversion
Converting Decimals to Percent	0.005 = 0.5% 0.23 = 23% 0.67 = 67% 2.17 = 217% 3.456 = 345.6%	multiply the decimal by 100 to change the decimal to a percent.
Converting Percent to Decimals	0.5% = 0.005 23% = 0.23 67% = 0.67 217% = 2.17 345.6% = 3.456	divide the percent by 100 to change the percent to a decimal Converting Percent to Decimal (1 - 100%)

Percent Calculation Methods

Cross Multiply Method

%/100 = is/of = i/o

cross multiply to solve:

% x of = 100 x is

Algebra.help -- Percentage Calculator

Word Translation method

What % of (number) is what?

x% x of = is

5% of 300 is what?

5/100 = i/300

cross multiply to solve:

5 x 300 = 100 x i

1500 = 100 i

i = 15

Algebra.help -- Percentage Calculator

5% of 300 is what?

5% x 300 = i

0.05 x 300 = i

i = 15

50% of what is 40?

50/100 = 40/o

cross multiply to solve:

50 x o = 100 x 40

50 o = 4000

o = 80

Algebra.help -- Percentage Calculator

50% of what is 40?

50% x o = 40

0.5 o = 40

o = 80

What % of 80 is 60?

x/100 = 60/80

cross multiply to solve:

80x = 100 x 60

80x = 6000

x = 75

Algebra.help -- Percentage Calculator

What % of 80 is 60?

x% x 80 = 60

x% = 60/80 = 0.75

x = 75%

Percent Problems
Example	Fraction	Decimal	Percent (%)
You get 3 bonus marks to make your total score 13 out of a test total of 10.	13/10	1.3	130%
The price of a pair of socks is increased from $1 to $3. What was the percent increase?	2/1	2.0	200%
The price of Online Math stock rises from $.50 to $200 per share. What was the percent increase?	199.50/0.5 = 399/1	399	39 900%
15 students tried out for the senior basketball team in 1999. 45 tried out in 2000. What was the percentage increase?	30/15 = 2/1	2	200%
The power bill was $30.00 in July and $75.99 in December. What was the percentage decrease.	45.99/30 = 1533/1000	1.533	153.3%