Chapter 1.7 Notes: Find Perimeter,
Circumference, and Area
Goal: You will find dimensions of polygons.
• Perimeter is the distance around a figure.
• Circumference is the distance around a circle.
• Area is the amount of surface covered by a figure.
• Perimeter and circumference are measured in units
of length, such as meters (m) and feet (ft).
• Area is measured in square units, such as square
meters (m2) and square feet (ft2).
• Formulas for Perimeter, Area, and Circumference:
• Square:
– Perimeter (P) = 4s
– Area (A) = s2
(s = side length)
• Rectangle:
– Perimeter (P) = 2L + 2w
– Area (A) = Lw
( L = length, w = width)
• Triangle:
– Perimeter (P) = a + b + c
a
b
– Area (A) = ½ bh
(for perimeter; side lengths of triangle a, b, c)
(for area; b = base, h = height)
• Circle:
– Circumference ( C) = πd or C = 2πr
– Area (A) = πr2
• Pi (π) is the ratio of a circle’s circumference to its
diameter.
Ex.1: Find the perimeter and area of the rectangular
basketball court shown.
Ex.2: Find the perimeter and area of the dining room
shown.
12 ft
9 ft
Ex.3: You are ordering circular cloth patches for your
soccer team’s uniforms. Find the approximate
circumference and area of the patch shown.
Ex.4: Find the approximate circumference and area of
the circular window shown.
(d = 18 in)
• Find the area and perimeter of the figure. If
necessary, round to the nearest tenth.
Ex.5:
1.6 cm
Ex.6: Triangle QRS has vertices Q(1, 2), R(4, 6), and
S(5, 2). What is the approximate perimeter of
triangle QRS?
Ex.7: Use the diagram below to answer (a) and (b).
a. Describe how to find the height from F to EG in
the triangle below.
b. Find the perimeter and the area of the triangle
shown below.
Ex.8: The base of a triangle is 28 meters. Its area is
308 square meters. Find the height of the triangle.
Ex.9: The base of a triangle is 14 cm. Its area is 42
cm2. Find the height of the triangle.
Ex.10: An ice-resurfacing machine is used to smooth
the surface of the ice at a skating rink. The machine
can resurface about 270 square yards of ice in one
minute.
About how many minutes does it take the machine
to resurface a rectangular skating rink that is 200
feet long and 90 feet wide?