Circumference and Area of a Circle

1. Radius $=9 cm$

Diameter $=18 cm$

2. Radius $=4.2 cm$

Diameter $=8.4 cm$

3. $=16$ units

4. $=8$ units

5. Radius $=6.5 cm$

Diameter $=13 cm$

6. Radius $=16 cm$

Diameter $=32 cm$

7.  $=4$ units

1. A circle has a circumference of $113.04$ units.

What is the diameter of the circle?

_______ units

2. A circle has a circumference of $452.16$ units.

What is the radius of the circle?

_______ units

3. What is the circumference of the following circle?

_______ units

4. Suppose the diameter of a circle is $16$ units. What is its circumference?

_______ units

1. The answer

The diameter is approximately 36 units.

2. The answer

The radius is approximately 72 units.

3. $\approx 6.28$ units

4. $\approx 50.24$ units

1. Find the area of a circle with a circumference of $31.4$ units.

_________ units $^{2}$

2. What is the area of the following circle?

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

_________ units $^{2}$

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

_________ units $^{2}$

4. Find the area of a circle with a circumference of $6.28$ units.

_________ units $^{2}$

5. Find the area of a circle with a radius of 2.

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

_________ units $^{2}$

6. Find the area of a circle with a diameter of 4.

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

_________ units $^{2}$

7.  Find the area of a circle with a circumference of $18.84$ units.

_________ units $^{2}$

1. $A \approx 25 \pi$

$A \approx 78.5 unit ^{2}$

2. $A=16 \pi$

3. $A=25 \pi$

4. $A \approx 1 \pi$

$A \approx 3.14$ unit $^{2}$

5. $A=4 \pi$

6. $A=4 \pi$

7.  $A \approx 9 \pi$

$A \approx 28.26$ unit $^{2}$

1. 

Find the arc length of the semicircle.

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

________ units

2. 

Find the arc length of the partial circle.

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

________ units

________ units

4. 

Find the arc length of the semicircle.

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal. units

________ units

1. The answer

The arc length of the semicircle is $4 \pi$ units.

(Note that we could also multiply 4 by $3.14$ to get $12.56$ units.)

2. The answer

The arc length of the partial circle is $3.5 \pi$ units.

(Note that we could also multiply $3.5$ by $3.14$ to get $10.99$ units.)

3. The answer

The arc length of the partial circle is $\frac{1}{2} \pi$ units.

(Note that we could also multiply $\frac{1}{2}$ by $3.14$ to get $1.57$ units.)

4. The answer

The arc length of the semicircle is $6 \pi$ units.

(Note that we could also multiply 6 by $3.14$ to get $18.84$ units.)

1. 

Find the area of the shape.

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

________ units $^{2}$

2. 

Find the area of the semicircle.

Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

________ units $^{2}$

3. 

Find the area of the semicircle.
Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

________ units $^{2}$

4. 

Find the area of the shape.
Either enter an exact answer in terms of $\pi$ or use $3.14$ for $\pi$ and enter your answer as a decimal.

________ units $^{2}$

1. The answer

The area of the shape is $3 \pi$ units $^{2}$.

(Note that we could also multiply 3 by $3.14$ to get $9.42$ units $^{2}$.)

2. The answer

The area of the semicircle is $12.5 \pi$ units $^{2}$.

(Note that we could also multiply $12.5$ by $3.14$ to get $39.25$ units $^{2}$.)

3. The answer

The area of the semicircle is $4.5 \pi$ units $^{2}$.

(Note that we could also multiply $4.5$ by $3.14$ to get $14.13$ units $^{2}$.)

4. The answer

The area of the shape is $12 \pi$ units $^{2}$.

(Note that we could also multiply 12 by $3.14$ to get $37.68$ units $^{2}$.)