Measuring Circles

A circle has a diameter of 5 cm. What is the area of the circle?

• 7.85 cm

• 15.7 cm

• 19.625 cm

• 31.4 cm

Complete the following statement.

Pi (π) is the ratio of the ​ (a)   of a circle to its ​ (b)  

• circumference
• diameter

For each quantity, decide whether circumference or area would be needed to calculate it.

1. The distance around a circular track. ​ (a)  

2. The amount of oil it takes to cover the bottom of a frying pan. ​ (b)  

3. The distance your car will go with one turn of the wheels. ​ (c)   ​

• Circumference
• Area

A circle has a radius of 30 cm. What is the circumference of the circle?

• 2.826 cm

• 188.4 cm

• 94.2 cm

• 47.1 cm

A groundskeeper needs grass seed to cover a small circular field, 20 feet in diameter.

 A store sells 10-pound bags of grass seed that cover 200 square feet. 

 What is the smallest number of bags the groundskeeper must buy to cover the circular field?  

To solve this problem, you would calculate the ​ (a)   and not the ​ (b)   .

• area
• circumference

A groundskeeper needs grass seed to cover a small circular field, 20 feet in diameter.

 A store sells 10-pound bags of grass seed that cover 200 square feet. 

If the area is 314 square feet, how many bags of see will you need to purchase?

The students in Mr. Rivera's art class are designing a stained-glass window to hang in the school entryway. The window will be 4 feet tall and 10 feet wide.

To find out how many square feet of clear glass will be needed for the window, do you solve for area or circumference?

How many circles are in this picture?

If the height is 4, and the length is 10, what is the diameter of each circle?