Find the perimeter of the figure. Round

to the nearest tenth if necessary.

Find the perimeter of the figure. Round

to the nearest tenth if necessary.

The area of an obtuse triangle is 52.92 square centimeters. The base of the triangle is 12.6 centimeters. What is the height of the triangle?

13(2) + 11(2) = 48 cm

10 + 17.9 + 10 = 37.9 ft

52.92 = 12.6h h = 8.4 cm 2

Ch 10.4

Ch 10.4(2)Areas of Trapezoids

Standard 10.0Students compute areas of polygons.

Learning Target:I will be able to find the areas of trapezoids.

Ch 10.4

Ch 10.4

Theorem 10-4

Area of a Trapezoid

SHAVING Find the area of steel used to make the side of the razor blade shown below.

Area of a trapezoid

h = 1, b1 = 3, b2 = 2.5

Simplify.

Answer: A = 2.75 cm2

Ch 10.4

A. 288 ft2

B. 295.5 ft2

C. 302.5 ft2

D. 310 ft2

Find the area of the side of the pool outlined below.

Ch 10.4

OPEN ENDED Miguel designed a deck shaped like the trapezoid shown below. Find the area of the deck.

Read the Test Item

You are given a trapezoid with one base measuring 4 feet, a height of 9 feet, and a third side measuring 5 feet. To find the area of the trapezoid, first find the measure of the other base.

Ch 10.4

Solve the Test Item

Draw a segment to form a right triangle and a rectangle. The triangle has a hypotenuse of 5 feet and legs of ℓ and 4 feet. The rectangle has a length of 4 feet and a width of x feet.

Ch 10.4

OPEN ENDED Miguel designed a deck shaped like the trapezoid shown below. Find the area of the deck.

Use the Pythagorean Theorem to find ℓ.

a2 + b2 = c2 Pythagorean Theorem

42 + ℓ2 = 52 Substitution

16 + ℓ2 = 25 Simplify.

ℓ2 = 9 Subtract 16 from each side.

ℓ = 3 Take the positive square rootof each side.

Ch 10.4

By Segment Addition, ℓ + x = 9. So, 3 + x = 9 and x = 6. The width of the rectangle is also the measure of the second base of the trapezoid.

Area of a trapezoid

Substitution

Simplify.Answer: So, the area of the deck is 30 square feet.

Ch 10.4

Check

The area of the trapezoid is the sum of the areas of

the areas of the right triangle and rectangle. The area

of the triangle is or 6 square feet. The area of

the rectangle is (4)(6) or 24 square feet. So, the area

of the trapezoid is 6 + 24 or 30 square feet.

Ch 10.4

A. 58 ft2

B. 63 ft2

C. 76 ft2

D. 88 ft2

Ramon is carpeting a room shaped like the trapezoid shown below. Find the area of the carpet needed.

Ch 10.4

A. 3 yd

B. 6 yd

C. 2.1 yd

D. 7 yd

Trapezoid QRST has an area of 210 square yards. Find the height of QRST.

Ch 10.4

Ch 10.4