Ratio and Proportion
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A ratio is the mathematical comparison of one number to another. Examples are as follows:
- 5 to 1 or 5:1
- 6 to 3 or 6:3 (Simplified - 2:1)
- 4 to 3 or 4:3
- 8 to 6 or 8:6 (Simplified - 4:3)
- 3/4 or 3:4
- 5/4 or 5:4
Ordinary fractions can be considered to be ratios.
Proportion
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A proportion is the statement that one ratio equals another ratio.
- 4 is to 6 as 2 is to 3 or 4:6 = 2:3
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To verify that this is correct, cross multply.numerator 1 with denominator 2 and denominator 1 with numerator 2. If the proportion be correct, the two products will be the same.
4 x 3 = 12
6 x 2 = 12 - Problem -- 1: 4 is to what as 16 is to 25?
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Let the unknown number = Y.
4/Y = 16/24
4 x 24 = Y x 16
16Y = 96
16Y ÷ 16 = 96 ÷ 16
Y = 6 - Problem -- You are 20 years old and are 2/3 the age of your sister, how old is your sister?
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Let your sister's age = Y.
20/Y = 2/3
2Y = 60
2Y ÷ 2 = 60 ÷ 2
Y = 30
Your sister's age = 30.
