solving Proportions using Cross-Products

Solving Proportions using Cross-Products

Proportions

• comparison between two ratios

• can be equal or not

• cross-products (butterfly) can be used to determine if they are equal

BUT... what do you do if one of the numbers in the proportion is missing?

Cross-multiply to write an equation.

 $\frac{x}{4}=\frac{10}{12}$  

 $\frac{9}{y}=\frac{3}{17}$  

 $\frac{12}{10}=\frac{a}{15}$  

 $\frac{w}{6}=\frac{6}{9}$  

Multiple Choice

Solve.

• y = 8

• y = 1/8

• y = 40

Multiple Choice

Solve the proportion:

• 4
• 8
• 14
• 10

Multiple Choice

Solve the proportion.

• p=31.3
• p=308
• p=924
• p=532

Multiple Choice

• 2.5
• 1
• 3.25
• -2.25

Multiple Choice

• 6.25
• 16
• 4
• 3.6