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What Are You Learning? I CAN solve proportions. 2

Why Do You Need To Know This?  Proportions can be used to compare different types of items.  Proportions are useful because they allow objects to be compared equally.  They can be used many ways in the real world. 3

Vocabulary  Proportion—an equation that shows that two ratios are equivalent.  Cross Product—the product of the numerator of one ratio and the denominator of the other ratio. 4

Notes 1 = x 6 is a cross product. 2 x 3 is a cross product.  The cross products of a proportion are equal.  Two ratios form a proportion if their cross products are equal. 5

Determine whether each pair of ratios form a proportion. a. ¾ and 9/12 b. 8/12 and 14/21 c. 4/5 and 5/6 d. 25/40 and 5/8 e. 13/15 and 4/5 f. 49/21 and 28/12 6

Notes  Solving the proportion— Process of using cross products to find a missing term in a proportion.  Solving a proportion is similar to solving an equation. 7

Example x = x 6 = 9 4 (Cross multiply) 6x = 36 (Solve for the variable) 6x = 36 (Divide to undo multiplication 6 6 x = 6 8

Solve each proportion. When necessary, round to the nearest tenth. a. 15/30 = n/34 b. h/36 = 21/27 c. 26/15 = 130/m d. 36/j = 7/20 e. r/23 = 17/34 f. 77/93 = x/24 9