HSPT Math : How to find the perimeter of a figure

Study concepts, example questions & explanations for HSPT Math

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Example Questions

Example Question #59 : Geometry

What is the perimeter of a square with a side length of \(\displaystyle a-1\)?

Possible Answers:

\(\displaystyle 4a^2-4\)

\(\displaystyle a^2-4\)

\(\displaystyle a-4\)

\(\displaystyle 4a+4\)

\(\displaystyle 4a-4\)

Correct answer:

\(\displaystyle 4a-4\)

Explanation:

Write the perimeter formula for a square.

\(\displaystyle P=4s\)

Substitute the side length in the formula and simplify.

\(\displaystyle P=4(a-1)= 4a-4\)

Example Question #12 : How To Find The Perimeter Of A Figure

A circle has radius 8. The circumference of the circle is 40% of what number?

Possible Answers:

\(\displaystyle 25 \pi\)

\(\displaystyle 40 \pi\)

\(\displaystyle 2 0 \pi\)

\(\displaystyle 80 \pi\)

Correct answer:

\(\displaystyle 40 \pi\)

Explanation:

The circumference of a circle is its radius mulitplied by \(\displaystyle 2 \pi\). The radius is 8, so the circumference is 

\(\displaystyle 8 \cdot 2 \pi = 16 \pi\).

To find the number of which this is 40%, divide this by 40%, or \(\displaystyle \frac{40 }{100}\):

\(\displaystyle 16 \pi \div\frac{40 }{100} = 16 \pi \div\frac{2}{5} = 16 \pi \cdot \frac{5} {2} = \frac{80 \pi} {2} = 40 \pi\)

Example Question #262 : Problem Solving

\(\displaystyle \bigtriangleup ABC \sim \bigtriangleup DEF\).

\(\displaystyle \angle B\) is a right angle.

\(\displaystyle m \angle C = 45 ^{\circ }\).

Is \(\displaystyle \bigtriangleup DEF\) scalene, isosceles, or equilateral - or can it be determined?

Possible Answers:

Whether \(\displaystyle \bigtriangleup DEF\) is scalene, isosceles, or equilateral cannot be determined.

\(\displaystyle \bigtriangleup DEF\) is an equilateral triangle.

\(\displaystyle \bigtriangleup DEF\) is a isosceles triangle, but not equilateral.

\(\displaystyle \bigtriangleup DEF\) is a scalene triangle.

Correct answer:

\(\displaystyle \bigtriangleup DEF\) is a isosceles triangle, but not equilateral.

Explanation:

Corresponding angles of similar triangles are congruent, so 

\(\displaystyle m \angle E = m \angle B = 90 ^{\circ }\)

\(\displaystyle m \angle F = m \angle C = 45 ^{\circ }\)

The degree measures of the angles of a triangle total 180, so

\(\displaystyle m \angle D =180^{\circ } - (m \angle F +m \angle E )\)

\(\displaystyle m \angle D =180^{\circ } - (90^{\circ } +45^{\circ } ) = 45^{\circ }\)

Since \(\displaystyle \angle D\) and \(\displaystyle \angle F\) are congruent, by the Isosceles Triangle Theorem, 

\(\displaystyle \overline{EF} \cong \overline{DE}\)

making \(\displaystyle \bigtriangleup DEF\) isosceles.

Example Question #263 : Problem Solving

A ladder 30 feet long leans against a house. The top of the ladder is \(\displaystyle N\) feet above the ground. In terms of \(\displaystyle N\), how far along the ground is the bottom of the ladder from the house?

Possible Answers:

\(\displaystyle 30 + N\)

\(\displaystyle \sqrt{900 + N^{2}}\)

\(\displaystyle \sqrt{900 - N^{2}}\)

\(\displaystyle 30 - N\)

Correct answer:

\(\displaystyle \sqrt{900 - N^{2}}\)

Explanation:

The ladder, which is 30 feet long, is the hypotenuse of a right triangle whose legs are the line from the top of the ladder to the ground, which has length \(\displaystyle N\) feet, and the line from the bottom of the ladder horizontally to the house, whose length we will call \(\displaystyle M\) feet. See the diagram below.

Ladder

 

 

 

 

By the Pythagorean Theorem,

\(\displaystyle M^{2}+N^{2} = 30 ^{2} = 900\)

Solving for \(\displaystyle M\):

\(\displaystyle M^{2}+N^{2} - N^{2} = 900 - N^{2}\)

\(\displaystyle M^{2}= 900 - N^{2}\)

\(\displaystyle M = \sqrt{900 - N^{2}}\), the correct choice.

Example Question #6 : Parallelograms

What is the perimeter of the polygon below? 

A

 

Possible Answers:

\(\displaystyle 46in\)

\(\displaystyle 43in\)

\(\displaystyle 48in\)

\(\displaystyle 45in\)

\(\displaystyle 47in\)

Correct answer:

\(\displaystyle 48in\)

Explanation:

To find the area of a perimeter, we add all of the side lengths together. 

\(\displaystyle 9+15+6+8+3+7=48\)

Example Question #7 : Parallelograms

What is the perimeter of the polygon below? 

B

 

Possible Answers:

\(\displaystyle 38in\)

\(\displaystyle 32in\)

\(\displaystyle 33in\)

\(\displaystyle 31in\)

\(\displaystyle 30in\)

Correct answer:

\(\displaystyle 32in\)

Explanation:

To find the area of a perimeter, we add all of the side lengths together. 

\(\displaystyle 8+7+4+1+4+8=32\)

Example Question #12 : How To Find The Perimeter Of A Figure

What is the perimeter of the polygon below? 

C

 

Possible Answers:

\(\displaystyle 41in\)

\(\displaystyle 42in\)

\(\displaystyle 44in\)

\(\displaystyle 43in\)

\(\displaystyle 40in\)

Correct answer:

\(\displaystyle 42in\)

Explanation:

To find the area of a perimeter, we add all of the side lengths together. 

\(\displaystyle 12+5+8+4+4+9=42\)

Example Question #61 : Geometry

What is the perimeter of the polygon below? 

D

 

Possible Answers:

\(\displaystyle 54in\)

\(\displaystyle 53in\)

\(\displaystyle 51in\)

\(\displaystyle 52in\)

\(\displaystyle 55in\)

Correct answer:

\(\displaystyle 52in\)

Explanation:

To find the area of a perimeter, we add all of the side lengths together. 

\(\displaystyle 15+10+5+1+10+11=52\)

Example Question #62 : Geometry

What is the perimeter of the polygon below? 

E

 

Possible Answers:

\(\displaystyle 41in\)

\(\displaystyle 40in\)

\(\displaystyle 44in\)

\(\displaystyle 43in\)

\(\displaystyle 42in\)

Correct answer:

\(\displaystyle 40in\)

Explanation:

To find the area of a perimeter, we add all of the side lengths together. 

\(\displaystyle 8+12+4+6+4+6=40\)

Example Question #11 : Parallelograms

What is the perimeter of the polygon below? 

F

 

Possible Answers:

\(\displaystyle 37in\)

\(\displaystyle 35in\)

\(\displaystyle 36in\)

\(\displaystyle 38in\)

\(\displaystyle 34in\)

Correct answer:

\(\displaystyle 38in\)

Explanation:

To find the area of a perimeter, we add all of the side lengths together. 

\(\displaystyle 7+7+2+5+5+12=38\)

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