Circle Area, Circumference

I understand the difference between Circumference and Area of Circles.

• Area of a circle is the amount of space inside a circle, Circumference is the distance around a circle.

• Area and Circumference is easy for me.

• I need a bit of extra help on this topic.

• This is easy

What is the area of a circle if the circumference is 138.16?

Chris is sitting on the edge of a dock tossing rocks into the water. As each rock hits the water, small circles appear traveling outward from the point of impact. The radius of the circle is changing at a rate of 5 in/sec.  How fast is the area changing when the circumference is 4 in? 

• 40 in/sec

• 20 in/sec

• 20pi in/sec

• 40pi in/sec

The circumference of a circular garden is 24.73 ft. What is the area of the garden?

What is the area of a circle if the circumference is 94.2?

Oil spilled from a tanker spreads in a circle whose circumference increases at a rate of 40 ft/sec. How fast is the area of the spill increasing when the circumference of the circle is 100π ft?

What rate are we looking for and when?

Oil spilled from a tanker spreads in a circle whose circumference increases at a rate of 40 ft/sec. How fast is the area of the spill increasing when the circumference of the circle is 100π ft?

At what rate is the radius changing when the circumference is 100π ft?

The circumference of a circular horse pen is 94.24 ft. What is the area of the pen?