8-1 Ratios and Proportions

# 8-1 Ratios and Proportions - Equality of Cross Products For...

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Ratios & Proportions Ratios & Proportions Section 8-1

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ratio – a comparison of 2 quantities The ratio of a to b can be expressed as a:b or where b is not 0. b a
A special ratio often found in nature and used by artists and architects is the golden ratio . It is approximately 1: 1.618. The Fibonacci sequence is related to the golden ratio. Each term in the sequence is the sum of the 2 previous terms. (1,1,2,3,5,8,13,…)

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proportion – an equation stating that 2 ratios are equal eg. = The cross products of a proportion are equal. ( The product of the means equals the product of the extremes.) 4 3 8 6 4 3 8 6 = mean mean extreme extreme
Equality of Cross Products

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Unformatted text preview: Equality of Cross Products For any numbers a and c and any nonzero numbers b and d , iff ad = bc . b a = d c Properties of Proportions Properties of Proportions is equivalent to 1. ad = bc 2. 3. 4. a c b d = b d a c = a b c d = a b c d b d + + = Scale Drawing Scale Drawing In a scale drawing , the scale compares each length in the drawing to the actual length. The lengths used in a scale can be in different units. Example: 1 inch = 8 ft. Joke Time Joke Time How do you catch a “unique” rabbit? “Unique” up on him! How do you catch a “tame” rabbit? The “tame” way!...
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