Basic Mathematics for College Students

78. EASELS Refer to the figure below. What type of
    triangle studied in this section is used in the design of
    the legs of the easel?


79. POOL The rack shown below is used to set up the
    billiard balls when beginning a game of pool.
    Although it does not meet the strict definition of a
    polygon, the rack has a shape much like a type of
    triangle discussed in this section. Which type of
    triangle?


80. DRAFTING Among the tools used in drafting are
    the two clear plastic triangles shown below. Classify
    each according to the lengths of its sides and then
    according to its angle measures.

90°90°45° 60°

45°

30°

WRITING

81. In this section, we discussed the definition of a
    pentagon. What is thePentagon? Why is it named
    that?


82. A student cut a triangular shape out of blue
    construction paper and labeled the angles , ,
    and , as shown in figure (a) below. Then she tore
    off each of the three corners and arranged them as
    shown in figure (b). Explain what important
    geometric concept this model illustrates.


83. Explain why a triangle cannot have two right angles.


84. Explain why a triangle cannot have two obtuse
    angles.

REVIEW

85. Find 20% of 110.


86. Find 15% of 50.


87. What percent of 200 is 80?


88. 20% of what number is 500?


89. Evaluate:


90. FIRST AID When checking an accident victim’s
    pulse, a paramedic counted 13 beats during a
    15-second span. How many beats would be
    expected in 60 seconds?

0.852(0.25)

31

(a) (b)

2

1 3

2

 3

 1  2

746 Chapter 9 An Introduction to Geometry