Ratio and Proportion

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6.1 Ratios &
Proportion

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A RATIO is a quotient
that compare 2 quantities.
3
4
3 to 4 3 : 4
These are all the same.

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A Proportion is an equation
of two equal ratios.
gallons
miles
gallons
miles
2
25
4
50
=

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Proportion is true if
fractions are equal when in
lowest terms.
3 4 5
6 8 10
= =
all
reduce
to 1/2

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the Extremes.
the Means.
12
8
3
2
=

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The product of the means
equals the product of the
extremes.
Cross products are equal.
12
8
3
2
=
2 • 12 = 3 • 8
24 = 24

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To Solve Proportions
n
3
6
9
=
Find n
9 n = (3) (6)
9 n = 18
n = 2

8. fguilbert
7
4
=
w
5000 - w
7 ( 5000 - w) = 4 w
35,000 = 11 w
3182 = w
35000 - 7 w = 4 w

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3: 8 = n : 6
3 = n
8 6
18 = 8 n
18/8 = n
2.25 = n

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Similar Figures
A B
C D
E F
G H
Corresponding <s =
Sides are proportional

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A B
C D
E F
G H
ABCD ~ EFGH
10
12
13
Find GH small 10
big 13
= 12
GH

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small 10
big 13
= 12
GH
10 GH = (12)(13)
10 GH = 156
GH = 15.6
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A B
C D
E F
G H
ABCD ~ EFGH
110
Find m<E
<A = <E m<E = 1100
~
110

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A
B C
D
E F
AB C ~ DEF
8 6
5
Find EF

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A
B C
D
E F
AB C ~ DEF
8 6
5
small
big
6
8
= EF
5

16. fguilbert
6
8
= EF
5
x
(6)(5) = 8x
30 = 8x
30/8 = x
3.75 = x
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17. fguilbert
The desire to succeed
means nothing
without the
will to
prepare!
thought for the day