SAT Math : Plane Geometry

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #2 : How To Find The Length Of A Chord

Secant

Figure is not drawn to scale

In the provided diagram, the ratio of the length of  to that of  is 7 to 2. Evaluate the measure of .

Possible Answers:

Cannot be determined

Correct answer:

Cannot be determined

Explanation:

The measure of the angle formed by the two secants to the circle from a point outside the circle is equal to half the difference of the two arcs they intercept; that is,

The ratio of the degree measure of  to that of  is that of their lengths, which is 7 to 2. Therefore,

Letting :

Therefore, in terms of :

Without further information, however, we cannot determine the value of  or that of . Therefore, the given information is insufficient.

Example Question #1 : How To Find The Angle Of Clock Hands

It is 4 o’clock.  What is the measure of the angle formed between the hour hand and the minute hand?

Possible Answers:

Correct answer:

Explanation:

At four o’clock the minute hand is on the 12 and the hour hand is on the 4.  The angle formed is 4/12 of the total number of degrees in a circle, 360.

4/12 * 360 = 120 degrees

Example Question #1 : How To Find The Angle Of Clock Hands

If a clock reads 8:15 PM, what angle do the hands make?

Possible Answers:

Correct answer:

Explanation:

A clock is a circle, and a circle always contains 360 degrees. Since there are 60 minutes on a clock, each minute mark is 6 degrees.

The minute hand on the clock will point at 15 minutes, allowing us to calculate it's position on the circle.

Since there are 12 hours on the clock, each hour mark is 30 degrees.

We can calculate where the hour hand will be at 8:00.

However, the hour hand will actually be between the 8 and the 9, since we are looking at 8:15 rather than an absolute hour mark. 15 minutes is equal to one-fourth of an hour. Use the same equation to find the additional position of the hour hand.

We are looking for the angle between the two hands of the clock. The will be equal to the difference between the two angle measures.

Example Question #2 : How To Find The Angle Of Clock Hands

What is the measure of the smaller angle formed by the hands of an analog watch if the hour hand is on the 10 and the minute hand is on the 2?

Possible Answers:

56°

120°

45°

90°

30°

Correct answer:

120°

Explanation:

A analog clock is divided up into 12 sectors, based on the numbers 1–12. One sector represents 30 degrees (360/12 = 30). If the hour hand is directly on the 10, and the minute hand is on the 2, that means there are 4 sectors of 30 degrees between then, thus they are 120 degrees apart (30 * 4 = 120).

Example Question #3 : How To Find The Angle Of Clock Hands

At , what angle is between the hour and minute hand on a clock? 

Possible Answers:

Correct answer:

Explanation:

At , the hour hand is on the  and the minute hand is at the . There are  spaces on a clock, and these hands are separated by  spaces.

Thus, the angle between them is  the degrees of the entire clcok, which is .

Therefore, we multiply these to get our answer. 

 

We can cancel out as we multiply to get: 

 

Example Question #2 : How To Find The Angle Of Clock Hands

What is the measure, in degrees, of the acute angle formed by the hands of a 12-hour clock that reads exactly 3:10?

 

Possible Answers:

55°

65°

60°

35°

72°

Correct answer:

35°

Explanation:

The entire clock measures 360°. As the clock is divided into 12 sections, the distance between each number is equivalent to 30° (360/12). The distance between the 2 and the 3 on the clock is 30°.  One has to account, however, for the 10 minutes that have passed. 10 minutes is 1/6 of an hour so the hour hand has also moved 1/6 of the distance between the 3 and the 4, which adds 5° (1/6 of 30°). The total measure of the angle, therefore, is 35°.

 

 

Example Question #2 : How To Find The Angle Of Clock Hands

If it is 4:00, what is the measure of the angle between the minute and hour hands of the clock?

Possible Answers:

90 degrees

45 degrees

125 degrees

100 degrees

120 degrees

Correct answer:

120 degrees

Explanation:

A clock takes the shape of a circle, which is composed of 360 degrees. There are 12 numbers on a clock that represent the hours. With this in mind, we can say that each number represents an angle. The measure of the angle between each number is given by .

If it is 4:00, then the minute hand is pointing towards 12 while the hour hand points towards 4. 

Therefore, we can say that the angle between the two hands is  degrees. 

Another way to think of this is to imagine the clock at a nearby time. At 3:00, the hands of the clock form a right angle of 90 degrees. Since we know that each number on the clock is separated by 30 degrees, we can simply add 30 to 90 degrees and get 120 degrees for the angle at 4:00. 

Example Question #3 : How To Find The Angle Of Clock Hands

If it is 2:00 PM, what is the measure of the angle between the minute and hour hands of the clock?

Possible Answers:

45 degrees

120 degrees

30 degrees

60 degrees

90 degrees

Correct answer:

60 degrees

Explanation:

First note that a clock is a circle made of 360 degrees, and that each number represents an angle and the separation between them is 360/12 = 30. And at 2:00, the minute hand is on the 12 and the hour hand is on the 2.  The correct answer is 2 * 30 = 60 degrees.

Example Question #251 : Plane Geometry

Two pizzas are made to the same dimensions. The only difference is that Pizza 1 is cut into pieces at 30° angles and Pizza 2 is cut at 45° angles. They are sold by the piece, the first for $1.95 per slice and the second for $2.25 per slice. What is the difference in total revenue between Pizza 2 and Pizza 1?

Possible Answers:

$2.70

–$5.40

–$2.70

$5.40

$0

Correct answer:

–$5.40

Explanation:

First, let's calculate how many slices there are per pizza. This is done by dividing 360° by the respective slice degrees:

Pizza 1: 360/30 = 12 slices

Pizza 2: 360/45 = 8 slices

Now, the total amount made per pizza is calculated by multiplying the number of slices by the respective cost per slice:

Pizza 1: 12 * 1.95 = $23.40

Pizza 2: 8 * 2.25 = $18.00

The difference between Pizza 2 and Pizza 1 is thus represented by: 18 – 23.40 = –$5.40

Example Question #2 : Circles

A circular, 8-slice pizza is placed in a square box that has dimensions four inches larger than the diameter of the pizza. If the box covers a surface area of 256 in2, what is the surface area of one piece of pizza?

Possible Answers:

4.5π in2

36π in2

144π in2

9π in2

18π in2

Correct answer:

4.5π in2

Explanation:

The first thing to do is calculate the dimensions of the pizza box. Based on our data, we know 256 = s2. Solving for s (by taking the square root of both sides), we get 16 = s (or s = 16).

 

Now, we know that the diameter of the pizza is four inches less than 16 inches. That is, it is 12 inches. Be careful! The area of the circle is given in terms of radius, which is half the diameter, or 6 inches. Therefore, the area of the pizza is π * 62 = 36π in2. If the pizza is 8-slices, one slice is equal to 1/8 of the total pizza or (36π)/8 = 4.5π in2.

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