Which is the area of a circle with circumference of 15.7 units? ( use 3.14 for )

A = π(r²) --- r is radius

C = πd --- d is diameter

First, the circumference must be found. If the circumference is 15.7, plug it in.

15.7 = πd

We know what pi is.

15.7 = 3.14 (d)

Now, simply divide 3.14 by 15.7 to find the diameter (d). You get 5. Since the radius is half of the diameter, the radius is 2.5. Plug this into the area formula, and plug pi in, too.

A = 3.14(2.5²) 

2.5 to the second power is 6.25.

A = 3.14(6.25)

Tada! Multiply, and you're left with 19.625!