Intermediate Geometry : Plane Geometry

Study concepts, example questions & explanations for Intermediate Geometry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #11 : How To Find The Perimeter Of An Acute / Obtuse Triangle

Find the perimeter of the triangle below. Round to the nearest tenths place.

5

Possible Answers:

\displaystyle 9.6

\displaystyle 8.7

\displaystyle 11.2

\displaystyle 12.3

Correct answer:

\displaystyle 11.2

Explanation:

Draw in the height to create a right triangle.

5a

Now, using the relationship between the lengths of sides in a \displaystyle 30-60-90 triangle, where the long leg is the short leg times \displaystyle \sqrt 3 and the hypotenuse is two times the short leg, we can find out that the height of the triangle is \displaystyle \frac{3}{2} and the hypotenuse is \displaystyle 3.

The dashes on two sides of the triangle indicate that these two sides are congruent. The three side lengths of the triangle are \displaystyle 3, 3, \text{and }3\sqrt3.

Now, add up these side lengths to find the perimeter.

\displaystyle \text{Perimeter}=3+3+3\sqrt3=11.2

Example Question #11 : How To Find The Perimeter Of An Acute / Obtuse Triangle

Find the perimeter of the triangle below. Round to the nearest tenths place.

6

Possible Answers:

\displaystyle 32.4

\displaystyle 29.9

\displaystyle 23.8

\displaystyle 26.4

Correct answer:

\displaystyle 29.9

Explanation:

Draw in the height to create a right triangle.

6a

Now, using the relationship between the lengths of sides in a \displaystyle 30-60-90 triangle, where the long leg is the short leg times \displaystyle \sqrt3 and the hypotenuse is twice the length of the short leg, we can find out that the height of the triangle is \displaystyle 4 and the hypotenuse is \displaystyle 8.

The dashes on two sides of the triangle indicate that these two sides are congruent. The three side lengths of the triangle are \displaystyle 8, 8, \text{ and }8\sqrt3.

Now, add up these side lengths to find the perimeter.

\displaystyle \text{Perimeter}=8+8+8\sqrt3=29.9

Example Question #71 : Triangles

In terms of \displaystyle x, find the perimeter. 

8

Possible Answers:

\displaystyle 6x+2x\sqrt3

\displaystyle 4x+2x\sqrt3

\displaystyle 2x+2x\sqrt3

\displaystyle 8x+2x\sqrt3

Correct answer:

\displaystyle 4x+2x\sqrt3

Explanation:

Draw in the height to create a right triangle.

8a

Now, using the relationship between the lengths of sides in a \displaystyle 30-60-90 triangle, we can find out that the height of the triangle is \displaystyle x and the hypotenuse is \displaystyle 2x.

The ratio of the sides in a \displaystyle 30-60-90 triangle are: \displaystyle x:x\sqrt3:2x.

The dashes on two sides of the triangle indicate that these two sides are congruent. The three side lengths of the triangle are \displaystyle 2x, 2x, \text{ and }2x\sqrt3.

Now, add up these side lengths to find the perimeter.

\displaystyle \text{Perimeter}=2x+2x+2x\sqrt3=4x+2x\sqrt3

Example Question #14 : How To Find The Perimeter Of An Acute / Obtuse Triangle

In terms of \displaystyle x, find the perimeter.

9

Possible Answers:

\displaystyle 62x+42x\sqrt3

\displaystyle 84x+42x\sqrt3

\displaystyle 42x+42x\sqrt3

\displaystyle 84+42x\sqrt3

Correct answer:

\displaystyle 84x+42x\sqrt3

Explanation:

Draw in the height to create a right triangle.

9a

Now, using the relationship between the lengths of sides in a \displaystyle 30-60-90 triangle, we can find out that the height of the triangle is \displaystyle 21x and the hypotenuse is \displaystyle 42x.

The ratio of the sides in a \displaystyle 30-60-90 triangle are: \displaystyle x:x\sqrt3:2x.

The dashes on two sides of the triangle indicate that these two sides are congruent. The three side lengths of the triangle are \displaystyle 42x, 42x, \text{ and }42x\sqrt3.

Now, add up these side lengths to find the perimeter.

\displaystyle \text{Perimeter}=42x+42x+42x\sqrt3=84x+42x\sqrt3

Example Question #72 : Triangles

Find the perimeter of the triangle below. Round to the nearest tenths place.

7

Possible Answers:

\displaystyle 59.7

\displaystyle 58.3

\displaystyle 47.8

\displaystyle 59.1

Correct answer:

\displaystyle 59.7

Explanation:

Draw in the height to create a right triangle.

7a

Now, using the relationship between the lengths of sides in a \displaystyle 30-60-90 triangle, we can find out that the height of the triangle is \displaystyle 8 and the hypotenuse is \displaystyle 16.

The ratio of the sides in a \displaystyle 30-60-90 triangle are: \displaystyle x:x\sqrt3:2x.

The dashes on two sides of the triangle indicate that these two sides are congruent. The three side lengths of the triangle are \displaystyle 16, 16, \text{ and }16\sqrt3.

Now, add up these side lengths to find the perimeter.

\displaystyle \text{Perimeter}=16+16+16\sqrt3=59.7

Example Question #73 : Triangles

In terms of \displaystyle x, find the perimeter of the triangle.

10

Possible Answers:

\displaystyle 108x+36x\sqrt3

\displaystyle 72x+36x\sqrt3

\displaystyle 36x+36x\sqrt3

\displaystyle 72+36x\sqrt3

Correct answer:

\displaystyle 72x+36x\sqrt3

Explanation:

Draw in the height to create a right triangle.

15

Now, using the relationship between the lengths of sides in a \displaystyle 30-60-90 triangle, we can find out that the height of the triangle is \displaystyle 18x and the hypotenuse is \displaystyle 36x.

The ratio of the sides in a \displaystyle 30-60-90 triangle are: \displaystyle x:x\sqrt3:2x.

The dashes on two sides of the triangle indicate that these two sides are congruent. The three side lengths of the triangle are \displaystyle 36x, 36x, \text{ and }36x\sqrt3.

Now, add up these side lengths to find the perimeter.

\displaystyle \text{Perimeter}=36x+36x+36x\sqrt3=72x+36x\sqrt3

Example Question #512 : Intermediate Geometry

A triangle is defined by the following points on a coordinate plane: \displaystyle (1, 5), (2, 12), (-3, 4)

What is the perimeter of the triangle?

Possible Answers:

\displaystyle 21.67

\displaystyle 25.06

\displaystyle 22.49

\displaystyle 20.63

Correct answer:

\displaystyle 20.63

Explanation:

In order to find the perimeter of the triangle, we will first need to find the length of each side of the triangle by using the distance formula.

Recall the distance formula for a line:

\displaystyle \text{distance}=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}

The first side of the triangle is the line segment made with \displaystyle (1, 5)\text{ and }(2, 12) as its endpoints.

\displaystyle \text{side 1}=\sqrt{(2-1)^2+(12-5)^2}=\sqrt{50}=5\sqrt2

The second side of the triangle is the line segment that has \displaystyle (2, 12)\text{ and }(-3, 4) as its endpoints.

\displaystyle \text{side 2}=\sqrt{(2-(-3))^2+(12-4)^2}=\sqrt{89}

The third side of the triangle is the line segment that has \displaystyle (-3, 4)\text{ and }(1, 5) as its endpoints.

\displaystyle \text{side 3}=\sqrt{(1-(-3))^2+(5-4)^2}=\sqrt{17}

Now, add up these three sides with a calculator to find the perimeter of the triangle.

\displaystyle \text{Perimeter}=5\sqrt{2} +\sqrt{89}+\sqrt{17}=20.63

Make sure to round to \displaystyle 2 places after the decimal.

Example Question #511 : Plane Geometry

A triangle is defined by the following points in a coordinate plane: \displaystyle (5, 6), (7, 2), (9, 11).

What is the perimeter of the triangle?

 

Possible Answers:

\displaystyle 22.13

\displaystyle 26.78

\displaystyle 24.59

\displaystyle 20.09

Correct answer:

\displaystyle 20.09

Explanation:

In order to find the perimeter of the triangle, we will first need to find the length of each side of the triangle by using the distance formula.

Recall the distance formula for a line:

\displaystyle \text{distance}=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}

The first side of the triangle is the line segment made with \displaystyle (5, 6)\text{ and }(7, 2) as its endpoints.

\displaystyle \text{side 1}=\sqrt{(7-5)^2+(2-6)^2}=\sqrt{20}=2\sqrt5

The second side of the triangle is the line segment that has \displaystyle (7, 2)\text{ and }(9, 11) as its endpoints.

\displaystyle \text{side 2}=\sqrt{(9-7)^2+(11-2)^2}=\sqrt{85}

The third side of the triangle is the line segment that has \displaystyle (5, 6)\text{ and }(9, 11) as its endpoints.

\displaystyle \text{side 3}=\sqrt{(9-5)^2+(11-6)^2}=\sqrt{41}

Now, add up these three sides with a calculator to find the perimeter of the triangle.

\displaystyle \text{Perimeter}=2\sqrt{5} +\sqrt{85}+\sqrt{41}=20.09

Make sure to round to \displaystyle 2 places after the decimal.

Example Question #514 : Intermediate Geometry

A triangle is defined by the following points on a coordinate plane: \displaystyle (-5, 1), (6, -2), (7, 0).

What is the perimeter of the triangle?

Possible Answers:

\displaystyle 27.09

\displaystyle 28.81

\displaystyle 25.68

\displaystyle 30.01

Correct answer:

\displaystyle 25.68

Explanation:

In order to find the perimeter of the triangle, we will first need to find the length of each side of the triangle by using the distance formula.

Recall the distance formula for a line:

\displaystyle \text{distance}=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}

The first side of the triangle is the line segment made with \displaystyle (-5, 1)\text{ and }(6, -2) as its endpoints.

\displaystyle \text{side 1}=\sqrt{(6-(-5))^2+(-2-1)^2}=\sqrt{130}

The second side of the triangle is the line segment that has \displaystyle (6, -2)\text{ and }(7, 0) as its endpoints.

\displaystyle \text{side 2}=\sqrt{(7-6)^2+(0-(-2))^2}=\sqrt{5}

The third side of the triangle is the line segment that has \displaystyle (-5, 1)\text{ and }(7, 0) as its endpoints.

\displaystyle \text{side 3}=\sqrt{(7-(-5))^2+(0-1)^2}=\sqrt{145}

Now, add up these three sides with a calculator to find the perimeter of the triangle.

\displaystyle \text{Perimeter}=\sqrt{130} +\sqrt{5}+\sqrt{145}=25.68

Make sure to round to \displaystyle 2 places after the decimal.

Example Question #511 : Intermediate Geometry

A triangle is defined by the following points on a coordinate plane: \displaystyle (9, 8), (12, 0), (-1, -2).

What is the perimeter of the triangle?

Possible Answers:

\displaystyle 36.09

\displaystyle 31.45

\displaystyle 33.87

\displaystyle 35.84

Correct answer:

\displaystyle 35.84

Explanation:

In order to find the perimeter of the triangle, we will first need to find the length of each side of the triangle by using the distance formula.

Recall the distance formula for a line:

\displaystyle \text{distance}=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}

The first side of the triangle is the line segment made with \displaystyle (9, 8)\text{ and }(12, 0) as its endpoints.

\displaystyle \text{side 1}=\sqrt{(12-9)^2+(0-8)^2}=\sqrt{73}

The second side of the triangle is the line segment that has \displaystyle (12, 0)\text{ and }(-1, -2) as its endpoints.

\displaystyle \text{side 2}=\sqrt{(-1-12)^2+(-2-0)^2}=\sqrt{173}

The third side of the triangle is the line segment that has \displaystyle (9, 8)\text{ and }(-1, -2) as its endpoints.

\displaystyle \text{side 3}=\sqrt{(-1-9))^2+(-2-8)^2}=\sqrt{200}=10\sqrt2

Now, add up these three sides with a calculator to find the perimeter of the triangle.

\displaystyle \text{Perimeter}=\sqrt{73} +\sqrt{173}+10\sqrt{2}=35.84

Make sure to round to \displaystyle 2 places after the decimal.

Learning Tools by Varsity Tutors