Perimeter and Area

January 24, 2011

Perimeter

• Example 1 Find the Perimeter

• a. a square with a side length of 10 inches10 in.

P = 4s Perimeter formula

• = 4(10) Replace s with 10.

• = 40 Multiply.

• The perimeter is 40 inches.

10 in.

b. a rectangle with a length of 13 centimeters and a width of 4 centimeters P = 2( + w) = 2(13 + 4) = 13, w = 4 = 2(17) Add. = 34 Multiply.The perimeter is 34 centimeters.

13 cm

4 cm

• P = a + b + c Perimeter formula

• = 11 + 7 + 12 a = 11, b = 7, c = 12

• = 30 Add.

• The perimeter of the triangle is 30 meters.

11 m

12 m

7 m

25 yd

18 yd

P = 2(a + b) Perimeter formula= 2(18 + 25) a = 18, b = 25= 2(43) Add.= 86 Multiply.

The perimeter of the parallelogram is 86 yards.

• Find the circumference of each circle to the nearest tenth.

• a. The radius is 5 inches.

• C = 2r Circumference formula

• = 2(5) Replace r with 5.

• = 10 Simplify.

• The exact circumference is 10 feet.

• 10 ENTER 31.41592654

• The circumference is about 31.4 inches.

• b. The diameter is 22 meters.

• C = d Circumference formula

• = (22) Replace d with 22.

• = 22 Simplify. 69.1

• Use a calculator to evaluate 22.

• The circumference is about 69.1 meters.

Area

• a. a square that has a side length of 9 inches

• A = s² Area formula

• = 9² s = 9

• = 81 Multiply.

• The area is 81 square inches.

• b. a rectangle that has a length of 11 millimeters and a width of 4 millimeters

• A = w Area formula

• = 11(4) = 11, w = 4

• = 44 Multiply.

• The area of the rectangle is 44 square millimeters.

• a. a parallelogram that has a base of 30 feet and a height of 24 feet

• A = bh Area formula

• = 30(24) b = 30, h = 24

• = 720 Multiply.

• The area is 720 square feet.

24 ft

30 ft

a triangle that has a base of 13 kilometers and a height of 8 kilometers

8 km

13 km

A = bh Area formula = (13)(8) b = 13, h = 8 = 52 Multiply.The area is 52 square kilometers.

• . The radius is 4 miles.

• A = r² Area formula

• = (4) ² Replace r with 4.

• = 16 Simplify.

• 50.3 Use a calculator to evaluate 16.

• The area is about 50.3 square miles.

4 mi

• b. The diameter is 35 centimeters.

• A = r² Area formula

• = (17.5) ² Replace r with 17.5.

• = 306.25 Simplify.

• 962.1 Use a calculator to evaluate 306.25.

35 cm