7.1_Ratios_and_proportions.notebook
7.1 ­ Ratios and Proportions
February 23, 2010
What is a ratio?
Objective: To write ratios and solve proportions
Real ­ World Ratios
Example
• An F­15 aircraft produces 50,000 lb of thrust and weighs 44,500 lbs. What is its thrust­to­weight ratio? Write the ratio two different ways.
• Aspect ratio (width to height) of your TV/Computer screen
Widescreen TV's have an aspect ratio of 16:9
• Strength­to­weight ratio for materials • Thrust­to­weight ratio for an airplane
• Body Mass Index is a ratio of your
height to your weight squared
Proportions
Properties of Proportions
A proportion is a statement that two ratios are equal.
a c
It can be written as =
b d
Widescreen TV dimensions Write the proportionality statement for the TV dimensions (Width­to­height):
Screen width Screen height 46 " TV 40" 22.5" 55" TV 48" 27" 1
7.1_Ratios_and_proportions.notebook
Solving Proportions
1.
3.
2.
February 23, 2010
Applying Proportions
A recipe calls for 4 cups of flour and 6 eggs, but you only have 4 eggs. How much flour should you use?
4.
Scale Factor
A scale factor allows you to find the actual measurement from a scaled object or drawing.
Applying Scale Factors
The architecture drawing at the right shows a scale factor of 1 in. = 16 ft. The length of the bedroom in the drawing is 1.25 inches. What is the length of the actual bedroom? Homework
Pg. 369
#13 ­ 21 odd, 26, 27, 28
& 35 ­ 43 odd
2
Attachments
f­22.mp4