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Organize Binders -Move ch. 3 notes to “old notes” -Move review sheet to “review” -Move Quiz...
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Transcript of Organize Binders -Move ch. 3 notes to “old notes” -Move review sheet to “review” -Move Quiz...
Organize Binders-Move ch. 3 notes to “old notes”-Move review sheet to “review ”-Move Quiz to “quiz”-Throw away old homework
4-1 Ratios and Proportions
Objective: To determine if two ratios are equal and to solve proportions.
NEW STAMP LOG!
Vocabulary•Ratio: A comparison of 2 numbers using
division
▫Examples:
•Proportion: An equation stating that two ratios are equal
▫Examples:
22 :1 2 1
1to
5 1
10 23
4 2
x
Examples1. Write the ratio of “x to y”.
2. If there are 12 cats and 4 dogs, write the ratio of:1. Cats to Dogs
2. Dogs to Cats
Sidenote: You can (and should) reduce a ratio!!!
x
y
12
44
12
3
11
3
Comparing Ratios
•To tell if two ratios are equivalent (create a proportion), find the cross product.
6 22
8 28
6•28 8•22
168 176≠
Answer: Not a proportion
Proportion: We already know that the fractions are equal•Solve the Proportion
CROSS MULTIPLY
No more fractions!
6x
24 4x4
3
4 8
x
4
(8)(3) = (4)(x)
TOO: Watch your Negatives!!!
1) 2) 3)
Answers:1) r = 3/52) y = -13/43) x = -7/4
7 12
4 6
r r
2 5
6 2
y y
10 6
2 4x x