Warm-Up Solve each equation for x. 1) 3x = 5 2) 2x – 1 = 10 3) 5x + 3x = 14

Geometry 7-1 Ratios and Proportions

Definition A ratio compares two numbers by division. Ratios can be written 3 ways: 1) a to b2) a : b3) –b cannot equal zero because you can’t divide by 0 –The first number in “a to b” goes in the numerator of the fraction

Additional Note on Ratios A ratio can involve more than two numbers. For the rectangle, the ratio of the side lengths may be written as 3:7:3:7.

Example 1 Write a ratio expressing the slope of l.

Example 2 The ratio of the side lengths of a triangle is 4:7:5, and its perimeter is 96 cm. What is the length of the shortest side?

Example 3 The ratio of the angle measures in a triangle is 1:6:13. What is the measure of each angle?

Definition A proportion is an equation stating that two ratios are equal. Solve proportions using cross multiplication.

Examples Solve each proportion. 1) 2)

Re-Writing Proportions

Examples 1) Given that 18c = 24d, find the ratio of d to c in simplest form. 2) Given that 16s = 20t, find the ratio s:t in simplest form.