Common Core: 7th Grade Math : Grade 7

Study concepts, example questions & explanations for Common Core: 7th Grade Math

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Example Questions

Example Question #172 : Plane Geometry

The circumference of a circle is inches. Find the area of the circle.

Let .

Possible Answers:

Correct answer:

Explanation:

First we need to find the radius of the circle. The circumference of a circle is , where is the radius of the circle. 

 

The area of a circle is where   is the radius of the circle.

Example Question #1 : Radius

Screen_shot_2013-09-16_at_1.04.39_pm

The radius of a circle is 4 cm, what is the area?

Possible Answers:

Correct answer:

Explanation:

The area of a circle is found by: , where r is the radius.

.

The area of the circle is .

Example Question #1 : Plane Geometry

The radius, , of the circle below is 18 units. What is the area of the circle?

Circle

Possible Answers:

 square units

 square units

 square units

 square units

Cannot be determined

Correct answer:

 square units

Explanation:

The formula for the area, , of a circle with radius  is:

We can fill in 

You could do the arithmetic to get an area of about 1,017.876 square units, but it is ok and more precise to leave it as shown.

Example Question #1 : How To Find The Area Of A Circle

Give the area of a circle with diameter 13.

Possible Answers:

Correct answer:

Explanation:

Half of the diameter 13 is the radius . Use the area formula:

Example Question #25 : Radius

How many times greater is the area of a circle with a radius of 4in., compared to a circle with a radius of 2in.?

Possible Answers:

4

2\pi

4\pi

2

Correct answer:

4

Explanation:

The area of a circle can be solved using the equation A=\pi r^{2} 

The area of a circle with radius 4 is \pi 4^{2}=16\pi while the area of a circle with radius 2 is \pi 2^{2}=4\pi. 16\pi \div 4\pi =4

Example Question #42 : Basic Geometry

Find the area of a circle that has a radius of .

Possible Answers:

Correct answer:

Explanation:

Use the following formula to find the area of a circle:

For the circle in question, plug in the given radius to find the area.

In our particular case the radius is .

When squarring a fraction we need to square both the numerator and the denominator.

Example Question #43 : Basic Geometry

Find the area of a circle that has a radius of .

Possible Answers:

Correct answer:

Explanation:

Use the following formula to find the area of a circle:

For the circle in question, plug in the given radius to find the area.

In this problem the known radius is 

Now plug the radius into the area equation.

Therefore we get,

Recall that when a square root is squared you are left with the number under the square root sign. This happens because when you square a number you are multiplying it by itself. In our case this is,

.

From here we can use the property of multiplication and radicals to rewrite our expression as follows,

and when there are two numbers that are the same under a square root sign you bring out one and the other number and square root sign go away.

 

Example Question #941 : Grade 7

What is the area of a circle with a diameter of , rounded to the nearest whole number?

Possible Answers:

\dpi{100} 254

\dpi{100} 255

\dpi{100} 81

\dpi{100} 64

Correct answer:

\dpi{100} 64

Explanation:

The formula for the area of a circle is

\dpi{100} \pi r^{2}

Find the radius by dividing 9 by 2:

\dpi{100} \frac{9}{2}=4.5

So the formula for area would now be:

\dpi{100} \pi r^{2}=\pi (4.5)^{2}=20.25\pi \approx 63.6= 64

Example Question #141 : How To Find The Area Of A Circle

If this circle has a diameter of 12 inches, what is its area?

Circle_12d

Possible Answers:

None of the other answers are correct.

Correct answer:

Explanation:

To find the area, we need to determine the radius of the circle first.  

The radius is calculated as , where D is the diameter.

Given that the diameter is 12 inches, the radius is , or .

Next, we know that the formula for the area of the circle is .

Using the radius we just found, we can find the area:

Example Question #944 : Grade 7

What is the area of the circle provided? 

1

Possible Answers:

Correct answer:

Explanation:

In order to solve this problem, we need to recall the formula for the area of a circle: 

The circle in this question provides us with the radius, so we can use the formula to solve:

Solve:

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