With the area and circumference of a circle

Radius is 19.625
Divide 5 by 2 to get 2.5
Next multiply 2.5 by 2 to get 6.25
Then multiply 6.25 by 3.14 to get the answer

Circumference is 15.7
Multiply 3.14 by 5 to get the answer

Since we only know the diameter and the formulas use radius, we have to divide the diameter by two in both formulas. The trick is to remember the order of operations.

A= πr^2
A=(3.14)(5/2)^2
A=(3.14)(2.5)^2
A=(3.14)(6.25)
A=19.625 feet squared

Circumference=2πr
C=2(3.14)(5/2)
C=2(3.14)(2.5)
C=15.7 feet

Hope this helps! :)