Lesson 9-5

Example 1 Find a Missing Angle Measure

65°

x°

88°

92°

Find the value of x in the quadrilateral shown.
Since the sum of the angle measures in a quadrilateral is 360°, x + 65 + 88 + 92 = 360.

x + 65 + 88 + 92 = 360	Write the equation.
	x + 245 = 360	Add 65, 88, and 92.
	THINK What measure added to 245 equals 360?
	115 + 245 = 360	You know that 115 + 245 = 360.

So, the value of x is 115.

Example 2 Classify Quadrilaterals
DRAWINGS   Classify the quadrilaterals labeled 1 and 2 in the drawing.

Figure 1 is a parallelogram.
Figure 2 is a rectangle.

Example 3 Standardized Test Practice

x°

95°

85°

85°

GRIDDABLE What is the value of x in the parallelogram at the right?

9

5

Read the Test Item
You need to find the value of x.

Solve the Test Item
You know that in a parallelogram, opposite angles are congruent. Since the angle opposite the missing measure has a measure of 95°, x = 95.

Check 95 + 85 + 95 + 85 = 360°