This document contains notes from a math class on ratios and proportions. It includes definitions of ratios and proportions, examples of each, and practice problems for students to work on ratios, proportions, and setting up proportions to solve for unknown values. The teacher's agenda is also outlined, including covering ratios and proportions in class, having students complete an exit slip, returning tests, and working on homework if there is remaining time.

1. Geom8­1.notebook January 17, 2012
Math is black and white.
Everything else adds color, but you still need the paper.
!
date
and
er name
emb
Rem
BELL WORK: What is a ratio? What is a proportion? Are they
different or the same?
I will give you credit for this only if you attempt to answer. Give
me a sentence or two, not a word or two.
Agenda for the day:
• 8.1 Ratios and Proportions
• Exit Slip
• pass back papers and test
• go over test
• work on homework if time permits
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2. Geom8­1.notebook January 17, 2012
8.1 Ratios and Proportions
A ratio is a comparison of two different things; it is a quotient of two
numbers.
For example, how many guys are in this class? How many girls?
A ratio of the number of guys in the class compared to the number
of girls would be written:
The order in which you write the numbers of a ratio is important.
What is the ratio of girls to guys?
Another example:
Ratio of quarts to gallons?
Ratio of miles to feet?
Every ratio is equivalent to infinitely more ratios. Let's look back at
quarts to gallons.
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3. Geom8­1.notebook January 17, 2012
Slope as a ratio: 6
y
5
4
3
2
1
x
­6 ­5 ­4 ­3 ­2 ­1 0 1 2 3 4 5 6
­1
­2
­3
­4
­5
­6
15
14
13
5
12
11
4
10
9
8
3
7
6
Ratio as a map scale: 2
5
4
3
1
2
1
80°
0 0
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4. Geom8­1.notebook January 17, 2012
A proportion is an equation stating that two (or more) ratios are
equal.
You are able to solve a proportion, whereas you cannot solve a
ratios (because it is simply a fraction). Solving means that you are
missing part of 1 or both of the ratios.
P R oportion
Ex: Are the ratios 1:3 and 13:39 proportional?
Ex: Solve for x in order for the ratios 2 to 4 and 6 to x to be in proportion.
Ex: Solve the proportion. 3 7
=
x 14
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5. Geom8­1.notebook January 17, 2012
EXIT SLIP: What is the ratio of the number of diagonals in a pentagon
to the measure of each exterior angle of a regular decagon?
Label each step as to what you are doing. Don't just give me a
scramble of numbers with one circled somewhere.
Homework: p.329 #2,3,8,12,21
due Wednesday
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