Unit 3 Chapter 4 Section 4 Solving Proportions.notebook
December 15, 2014
Bellringer
1) Determine whether the ratios can form a proportion
a)
42 , 56
56 64
c)
5 , 30
4 24
b)
2 , 18
3 24
Jul 26­12:38 PM
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Unit 3 Chapter 4 Section 4 Solving Proportions.notebook
December 15, 2014
Unit 3
Chapter 4 Section 4
Solving Proportions
Objective: To solve proportions using unit rates, mental math and cross
products
There are more than one way to solve proportions.
In this section, we are going
to solve proportions using unit ratios, mental math
and cross product. You can
choose which way you like the best, but in certain
circumstances you may want to
use one over another.
Jun 6­8:17 PM
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Unit 3 Chapter 4 Section 4 Solving Proportions.notebook
December 15, 2014
There are many real­life applications for proportions. Can you name a few?
Medicine dosages are frequently related to the weight of the patient, so the dosage must be increased proportionally to weight.
Recipes or formulas may be increased or decreased by using proportions.
Maps, blueprints, and scale models. An appropriate ratio, or scale, is chosen. Large objects or areas can then be shown in a considerably smaller size or space. Movies frequently use scale models of ship, planes, buildings. Jul 1­12:56 PM
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Unit 3 Chapter 4 Section 4 Solving Proportions.notebook
December 15, 2014
Examples:
Using Unit Rates
1) You know the price of six oranges, but you want to buy eight. You can use solve a proportion to find the
total cost of the quantity that you want to buy. You can
use unit rates to solve a proportion. Step 1: Find the unit rate 2.34 dollars =
6 for $2.34
6 oranges
Step 2: Multiply to find the cost of 8 oranges
2) Postcards cost $2.45 for 5 cards. How much will 13 cards cost?
Using Mental Math
3) Solve each proportion using mental math.
z
21
=
a) 12
36
n
8
=
10
40
Using Cross Products
4) Solve each proportion using cross products.
a) 25 15
=
38 x
c)
b)
d)
16 d
=
30 51
12 x
=
15 21
20 110
=
35 m
Jun 10­10:28 AM
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Unit 3 Chapter 4 Section 4 Solving Proportions.notebook
December 15, 2014
Application:
Write and solve a proportion for each situation.
5) If 12 roses cost $18.96, what is the cost of 5 roses?
6) If 3 onions weigh 0.75 lb, how much do 10 onions weigh?
7) Franklin D. Roosevelt was elected president in 1932 with about 22,800,000 votes. The ratio of the number of votes he received to the number of votes the other candidates received was about 4 : 3. About how many votes did the other candidates receive?
Jul 1­12:37 PM
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Unit 3 Chapter 4 Section 4 Solving Proportions.notebook
December 15, 2014
Homework!
Check Your Understanding:
Pg 145, #'s 1­5
Jun 10­11:04 AM
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