PSAT Math : Plane Geometry

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #4 : How To Find The Length Of The Side Of A Right Triangle

A right triangle has two sides, 9 and x, and a hypotenuse of 15. What is x?

Possible Answers:

10

14

13

12

11

Correct answer:

12

Explanation:

We can use the Pythagorean Theorem to solve for x.

92 + x2 = 152

81 + x2 = 225

x2 = 144

x = 12

Example Question #1 : How To Find The Length Of The Side Of A Right Triangle

The area of a right traingle is 42. One of the legs has a length of 12. What is the length of the other leg?

Possible Answers:

7

9

6

11

5

Correct answer:

7

Explanation:

Area= \frac{1}{2}\times base\times height

42=\frac{1}{2}\times base\times 12

42=6\times base

base=7

Example Question #12 : How To Find The Length Of The Side Of A Right Triangle

Triangle

If  and , what is the length of ?

Possible Answers:

Correct answer:

Explanation:

AB is the leg adjacent to Angle A and BC is the leg opposite Angle A.

Since we have a  triangle, the opposites sides of those angles will be in the ratio .

Here, we know the side opposite the sixty degree angle. Thus, we can set that value equal to .

which also means

Example Question #81 : Triangles

Solve for x.

Possible Answers:

6

12

2

7

Correct answer:

6

Explanation:

Use the Pythagorean Theorem. Let a = 8 and = 10 (because it is the hypotenuse)

\small a^2+x^2=c^2

\small 8^2+x^2=10^2

\small 64+x^2=100

\small x^2=100-64=36

\small x=6

Example Question #462 : Geometry

Right_triangle

Note: Figure NOT drawn to scale.

Refer to the above diagram. Evaluate .

Possible Answers:

Correct answer:

Explanation:

The altitude perpendicular to the hypotenuse of a right triangle divides that triangle into two smaller triangles similar to each other and the large triangle. Therefore, the sides are in proportion. The hypotenuse of the triangle is equal to

Therefore, we can set up, and solve for  in, a proportion statement involving the shorter side and hypotenuse of the large triangle and the larger of the two smaller triangles:

Example Question #11 : Right Triangles

What is the hypotenuse of a right triangle with sides 5 and 8?

Possible Answers:

15

12

5√4

8√13

√89

Correct answer:

√89

Explanation:

Because this is a right triangle, we can use the Pythagorean Theorem which says a2 + b2 = c2, or the squares of the two sides of a right triangle must equal the square of the hypotenuse. Here we have a = 5 and b = 8.

a2 + b2 = c2

52 + 82 = c2

25 + 64 = c2

89 = c2

c = √89

Example Question #14 : Triangles

Trig_id

If  and , how long is side ?

Possible Answers:

Not enough information to solve

Correct answer:

Explanation:

This problem is solved using the Pythagorean theorem  .  In this formula  and  are the legs of the right triangle while  is the hypotenuse.

Using the labels of our triangle we have:

 

 

Example Question #21 : Right Triangles

If one of the short sides of a 45-45-90 triangle equals 5, how long is the hypotenuse?

Possible Answers:

5√2

√15

5

√10

π

Correct answer:

5√2

Explanation:

Using the Pythagorean theorem, x2 + y2 = h2. And since it is a 45-45-90 triangle the two short sides are equal. Therefore 52 + 52 = h2 .  Multiplied out 25 + 25 = h2.

Therefore h2 = 50, so h = √50 = √2 * √25 or 5√2.

Example Question #41 : Geometry

The height of a right circular cylinder is 10 inches and the diameter of its base is 6 inches. What is the distance from a point on the edge of the base to the center of the entire cylinder? 

Possible Answers:

None of the other answers

√(34)

√(43)/2

3π/4

4π/5

Correct answer:

√(34)

Explanation:

The best thing to do here is to draw diagram and draw the appropiate triangle for what is being asked. It does not matter where you place your point on the base because any point will produce the same result.  We know that the center of the base of the cylinder is 3 inches away from the base (6/2). We also know that the center of the cylinder is 5 inches from the base of the cylinder (10/2). So we have a right triangle with a height of 5 inches and a base of 3 inches. So using the Pythagorean Theorem 3+ 5= c2. 34 = c2, c = √(34).

Example Question #42 : Geometry

A right triangle with sides A, B, C and respective angles a, b, c has the following measurements. 

Side A = 3in. Side B = 4in. What is the length of side C? 

Possible Answers:

25

6

9

7

5

Correct answer:

5

Explanation:

The correct answer is 5. The pythagorean theorem states that a+ b= c2. So in this case 3+ 4= C2. So C= 25 and C = 5. This is also an example of the common 3-4-5 triangle. 

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