1. 5-1
Objective: Solving proportions

2. A ratio is the comparison of two numbers written as a fraction.
An equation in which two ratios are equal is called a proportion.
A proportion can be written using colon notation like this
a:b::c:d
Or as the more recognizable (and useable) equivalence of two fractions.

3. Proportions To set up a proportion think part/whole part ______ part=
whole
whole
If you can travel 120 miles on 6 gallons of gas, how far can you drive on 8 gallons of gas?
(6)gas
(8)gas
______
______
6x=960
x=160 =
120miles
(x) miles

4. RATIOS & PROPORTIONS Are the following proportions?
FALSE – Not a proportion
FALSE – Not a proportion
TRUE – this is a proportion
TRUE – this is a proportion

5. RATIOS & PROPORTIONS
Find the missing numbers to make the following proportions.

6. 5-2
Objective: Solve proportions involving scale drawings and models

7. SCALE DRAWINGS
A scale drawing is a drawing of an object with dimensions proportional to those of the actual object. To find lengths from scale drawings, set up and solve proportions.

9. SCALE DRAWINGS USING PROPORTIONS
EXAMPLE#1: ¼ in = 5 ft is a scale for a rock band’s concert stage.
A. The scale length of the drum stand is 1 in. What is the actual length of the drum stand?
Cross multiply.
Divide by .25

10. SCALE DRAWINGS USING PROPORTIONS
Given a scale of .5 in = 4 ft, find the actual length for each scale length given.

11. 5-3
Objective: Solve problems by using the percent equations

12. PERCENTS & DECIMALS Percent (%) means per hundred.
To change a decimal to a percent
Multiply the decimal by 100
Write a percent sign after it
Multiply the decimal by 100 (move the decimal point 2 places to the right)
Write a percent sign after it

13. To change a percent to a decimal
Divide the percent by 100
Omit the percent sign
Divide the percent by 100 (move decimal 2 places to the left)
Omit the percent sign

14. PERCENTS AND DECIMALS Convert the following decimals to percents:
44.5% A
15%
1.5% F
11.11% B
0.5%
62.5% G C
104.2% H
D. 0.9
90%

15. PERCENTS AND DECIMALS Convert the following percents to decimals:
0.015
A %
0.2345
0.25
F. 35%
0.35
B. 25%
0.125
G %
C %
3.1
H. 310%
D. 45%
0.45

16. The percent equation P r =
100 B
Percent
r (percentage) =
100
Base

17. Figuring out what goes where?
Remember is/of
“is” will always be “P”
“of” will always be “B”
What number is 15% of 10
What percent of 60 is 3 P 3 r r = =
100
100 10 60