Download Warm-Up

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 b
2) a : b
3)
– 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.