A13­4RatioProportion.notebook
September 11, 2013
Ratios and Rates
Algebra 1
Ch.3 Notes Page 12
P12 3­4 Ratio and Proportion
A ratio is a comparison of two numbers by division. a to b ; a:b ; a/b ; 2/3
A rate is a ratio that uses 2 different units
Dollars/Ounces
A UNIT rate is a rate with a denominator of 1. $.72/16oz = $.045/1oz
Sep 2­8:31 AM
Sep 13­9:59 AM
In 2004, Lance Armstrong won the Tour de France, completing the 3,391 km course in about 83.6 hours. Find Lance's unit rate. Cycling at his average speed, about how long would it take Lance to cycle 185 km?
Unit/Dimensional Analysis
Canceling Units in the TOP and BOTTOM of a Fraction
Dollars x Gallon
Gallon
Miles x Hour
Hour
mm x in x ft in ft yd
Aug 28­2:06 PM
Aug 28­1:59 PM
Converting from one set of units to another
Must have a CONVERSION FACTOR
Two things that are equal, but written in different units.
12in/1ft
60sec/1min
1mi/5280ft
Practice
Convert 45mi/1hr into inches/second
1in/2.54cm
Convert 5 years into hours
Aug 28­1:59 PM
Aug 28­1:59 PM
1
A13­4RatioProportion.notebook
September 11, 2013
To Solve Proportions...
Proportions
A proportion is an equation that states that two ratios are equal.
A = C
B D
AD = BC
5 = 10
8 16
AD = BC
Cross Multiply and Divide
4 = 12
x = 10
5 x
8 16
Are these Proportional???
3 = 10
8 11
Sep 16­8:15 AM
Sep 13­9:59 AM
Solving Multi­step Proportions...
Cross Multiply and Divide
HW #13
3­4 P145 #2,3,20­26,30,31,41,42,48­50,54
x + 4 = x ­ 2
5 7
3 = 5 x + 6 x ­ 4
Aug 28­2:33 PM
Please put your name and class period at the top of the homework.
Also include the homework number.
Aug 22­8:20 AM
2