SSAT Middle Level Math : Trapezoids

Study concepts, example questions & explanations for SSAT Middle Level Math

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Example Questions

Example Question #21 : Trapezoids

Q_10

Find the area of the trapezoid above.

Note: Image not drawn to scale.

Possible Answers:

\displaystyle 120\: cm^{2}

\displaystyle 160\: cm

\displaystyle 80\: cm

\displaystyle 120\: cm

\displaystyle 200\: cm^{2}

Correct answer:

\displaystyle 120\: cm^{2}

Explanation:

The area of a trapezoid is equal to the average of the length of the two bases multiplied by the height.

The formula to find the area of a trapezoid is: \displaystyle \left (\frac{base_{1} + base_{2}}{2}\right )* height 

In this problem, the lengths of the bases are \displaystyle 10\: cm and \displaystyle 20\: cm. Their average is \displaystyle 15\: cm. The height of the trapezoid is \displaystyle 8\: cm.

\displaystyle 15\: cm\ast 8\: cm=120\: cm

Remember: the answer to the problem should have units in cm2 .

Example Question #1 : How To Find The Area Of A Trapezoid

Find the area of a trapezoid with a height of \displaystyle 5\:cm and base lengths of \displaystyle 4\:cm and \displaystyle 8\:cm, respectively.

Possible Answers:

\displaystyle 22\:cm^{2}

\displaystyle 10\:cm^{2}

\displaystyle 30\:cm^{2}

\displaystyle 15\:cm^{2}

\displaystyle 17\:cm

Correct answer:

\displaystyle 30\:cm^{2}

Explanation:

The area \displaystyle A of a trapezoid is equal to the average of its two bases (\displaystyle b_{1} and \displaystyle b_{2}) multiplied by its height \displaystyle h. Therefore:

\displaystyle A=\frac{1}{2}(b_{1}+b_{2})h

\displaystyle A=\frac{1}{2}(4\:cm+8\:cm)5\:cm

\displaystyle A=30\:cm^{2}

Example Question #2 : How To Find The Area Of A Trapezoid

Find the area of a trapezoid with a height of \displaystyle 8\:cm and base lengths of \displaystyle 10\:cm and \displaystyle 12\:cm, respectively.

Possible Answers:

\displaystyle 30\:cm^{2}

\displaystyle 52\:cm^{2}

\displaystyle 30\:cm

\displaystyle 88\:cm

\displaystyle 88\:cm^{2}

Correct answer:

\displaystyle 88\:cm^{2}

Explanation:

The area \displaystyle A of a trapezoid is equal to the average of its two bases (\displaystyle b_{1} and \displaystyle b_{2}) multiplied by its height \displaystyle h. Therefore:

\displaystyle A=\frac{1}{2}(b_{1}+b_{2})h

\displaystyle A=\frac{1}{2}(10\:cm+12\:cm)8\:cm

\displaystyle A=88\:cm^{2}

Example Question #1 : How To Find The Area Of A Trapezoid

Trapezoid

 

What is the area of the above trapezoid?

Possible Answers:

\displaystyle 142.04\textrm{ m}^{2}

\displaystyle 109.18\textrm{ m}^{2}

\displaystyle 218.36\textrm{ m}^{2}

\displaystyle 76.32\textrm{ m}^{2}

\displaystyle 96.48\textrm{ m}^{2}

Correct answer:

\displaystyle 109.18\textrm{ m}^{2}

Explanation:

To find the area of a trapezoid, multiply one half (or 0.5, since we are working with decimals) by the sum of the lengths of its bases (the parallel sides) by its height (the perpendicular distance between the bases). This quantity is

\displaystyle A = 0.5 \cdot (7.2 + 13.4) \cdot 10.6 =0.5 \cdot 20.6 \cdot 10.6 = 109.18\textrm{ m}^{2}

Example Question #1 : How To Find The Area Of A Trapezoid

Find the area of the trapezoid:

Question_7

Possible Answers:

\displaystyle 49

\displaystyle 35

\displaystyle 28

\displaystyle 56

Correct answer:

\displaystyle 28

Explanation:

The area of a trapezoid can be determined using the equation \displaystyle A=\frac{1}{2}(b_1+b_2)h.

\displaystyle A=\frac{1}{2}(6+8)(4)

\displaystyle A=\frac{1}{2}(14)(4)

\displaystyle A=(7)(4)=28

Example Question #2 : How To Find The Area Of A Trapezoid

Trapezoid

 

What is the area of the trapezoid?

Possible Answers:

\displaystyle 105\textrm{ m}^{2}

\displaystyle 99\textrm{ m}^{2}

\displaystyle 63\textrm{ m}^{2}

\displaystyle 198\textrm{ m}^{2}

\displaystyle 135\textrm{ m}^{2}

Correct answer:

\displaystyle 99\textrm{ m}^{2}

Explanation:

To find the area of a trapezoid, multiply the sum of the bases (the parallel sides) by the height (the perpendicular distance between the bases), and then divide by 2.

\displaystyle A = \frac{1}{2} \cdot (7 + 15) \cdot 9 = \frac{1}{2} \cdot 22 \cdot 9 = 99 \textrm{ m}^2

Example Question #2 : How To Find The Area Of A Trapezoid

Trapezoid

The above diagram depicts a rectangle \displaystyle RECT with isosceles triangle \displaystyle \Delta ECM. If \displaystyle M is the midpoint of \displaystyle \overline{CT}, and the area of the orange region is \displaystyle 72, then what is the length of one leg of \displaystyle \Delta ECM ?

Possible Answers:

\displaystyle \sqrt {108}

\displaystyle \sqrt {54}

\displaystyle \sqrt {96}

\displaystyle 6

\displaystyle \sqrt {48}

Correct answer:

\displaystyle \sqrt {48}

Explanation:

The length of a leg of \displaystyle \Delta ECM is equal to the height of the orange region, which is a trapezoid. Call this length/height \displaystyle h.

Since the triangle is isosceles, then \displaystyle CM = h, and since \displaystyle M is the midpoint of \displaystyle \overline{CT}, \displaystyle MT = h. Also, since opposite sides of a rectangle are congruent, 

\displaystyle RE = CT = CM + MT = h + h = 2h

Therefore, the orange region is a trapezoid with bases \displaystyle h and \displaystyle 2h and height \displaystyle h. Its area is 72, so we can set up and solve this equation using the area formula for a trapezoid:

 \displaystyle \frac{1}{2} (B + b)h = 72

\displaystyle \frac{1}{2} (2h + h)h = 72

\displaystyle \frac{1}{2} (3h )h = 72

\displaystyle \frac{3}{2}h^{2} = 72

\displaystyle \frac{3}{2}h^{2} \cdot \frac{2}{3} = 72 \cdot \frac{2}{3}

\displaystyle h^{2}= 48

\displaystyle h = \sqrt {48}

This is the length of one leg of the triangle.

Example Question #3 : How To Find The Area Of A Trapezoid

A trapezoid has a height of \displaystyle 25 inches and bases measuring \displaystyle 24 inches and \displaystyle 36 inches. What is its area?

Possible Answers:

\displaystyle 600\; \textrm{in}^{2}

\displaystyle 750\; \textrm{in}^{2}

\displaystyle 1,500\; \textrm{in}^{2}

\displaystyle 900\; \textrm{in}^{2}

\displaystyle 864\; \textrm{in}^{2}

Correct answer:

\displaystyle 750\; \textrm{in}^{2}

Explanation:

Use the following formula, with \displaystyle B = 36,b = 24,h=25:

\displaystyle A = \frac{1}{2} (B+b)h = \frac{1}{2} (36+24) \cdot 25 = 750

Example Question #2 : How To Find The Area Of A Trapezoid

What is the area of a trapezoid with height 20 inches and bases of length 100 and 200? 

Possible Answers:

\displaystyle 6,000\; \textrm{in}^{2}

\displaystyle 3,000\; \textrm{in}^{2}

\displaystyle 4,000\; \textrm{in}^{2}

\displaystyle 1,000\; \textrm{in}^{2}

\displaystyle 2,000\; \textrm{in}^{2}

Correct answer:

\displaystyle 3,000\; \textrm{in}^{2}

Explanation:

Set  \displaystyle B=200\displaystyle b=100\displaystyle h = 20

The area of a trapezoid can be found using this formula:

\displaystyle A = \frac{1}{2} (B+b)h = \frac{1}{2} (200+100) \cdot 20 = 3,000

The area is 3,000 square inches.

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