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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