SAT Math : Pentagons

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #11 : Geometry

Pentagon

The above diagram shows a pentagonal track with perimeter one third of a mile. Adrianne starts at Point A and runs clockwise until she gets halfway between Points D and E. Which of the following choices is closest to the number of feet she runs?

Possible Answers:

1,200 feet

1,400 feet 

1,000 feet

1,300 feet

1,100 feet

Correct answer:

1,200 feet

Explanation:

The perimeter of the pentagonal track is one third of a mile; one mile is equal to 5,280 feet, so the perimeter is 

\displaystyle \frac{1}{3} \times 5, 280 = 1,760 feet.

Each side of the pentagon has length one fifth of its perimeter, or

\displaystyle \frac{1}{5} \times 1,760 = 352 feet.

Adrianne runs three and one half sides, or

\displaystyle 3 \frac{1}{2} \times 352 = 1,232 feet.

This makes 1,200 feet the closest, and correct, choice.

Example Question #1 : Pentagons

Pentagon

Aristotle High School has an unusual track in that it is shaped like a regular pentagon. Each side of the pentagon measures 264 feet.

Benny runs at a steady speed of eight miles an hour for ten minutes, starting at point A and working his way clockwise. When he is finished, which of the following points is he closest to?

Possible Answers:

Point E

Point A

Point D

Point B

Point C

Correct answer:

Point C

Explanation:

Benny runs at a rate of eight miles an hour for ten minutes, or \displaystyle \frac{10}{60} = \frac{1}{6} hours. The distance he runs is equal to his rate multiplied by his time, so, setting\displaystyle r = 8 , t = \frac{1}{6} in this formula:

\displaystyle d = rt

\displaystyle d = 8 \cdot \frac{1}{6} = \frac{4}{3} miles.

One mile comprises 5,280 feet, so this is equal to 

\displaystyle \frac{4}{3} \cdot 5,280 = 7,040 feet.

Since each side of the track measures 264 feet, this means that Benny runs 

\displaystyle 7,040 \div 264 = 26 \frac{2}{3} sidelengths.

This means Benny runs around the track for 25 sidelengths, which is 5 complete times, back to Point A; he then runs one more complete sidelength to Point B; and, finally, he runs \displaystyle \frac{2}{3} of a sidelength, finishing closest to Point C.

Example Question #11 : Sat Mathematics

Find the sum of all the angles in a pentagon.

Possible Answers:

\displaystyle 540

\displaystyle 720

\displaystyle 900

\displaystyle 360

Correct answer:

\displaystyle 540

Explanation:

To solve, simply use the formula to find the total degrees in a polygon, where n is thenumber of vertices.

In this particular case, a pentagon is a shape that has five sides and thus has five vertices.

Thus,

\displaystyle degrees=(n-2)*180=(5-2)*180=3*180=540

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