Can you discuss the differences between circumference and area of a circle ?

The circumference of a circle is the length around the circle which is equal to 360°. Pi is the number needed to find the circumference of the circle. In circles the AREA is equal to 3.14xRadias^2

The circumference (C) of any circle is the perimeter around it; it is circles' one dimensional measurement (i.e. in, ft, cm, mi, etc.). As a circle grows, increasing the
circle's size, the distance around it (circumference) increases proportionately with
the radius. Thus this length can be found by multiplying the radius × 2 (or diameter × 1) × a constant known as pi. Pi, an infinitely long decimal that begins 3.1416, was calculated by working backwards from the length of a circle, divided by 2×radius. No matter the size of any circle, they discovered that the distance will always vary 3.1416... × twice the radius (or diameter). An example is a circle of radius 40 cm: C = 2pi×r = 80pi cm, or 251.33 cm.

The area (A) of a circle, however, covers much more matter; it is the two dimensional measure of any circle (i.e. sq.in., sq.ft, sq.cm, etc.). Area also varies according the constant pi × the radius, BUT it increases much more than the radius once; it varies by the radius × radius (radius squared) × the value pi. Using the same circle example of radius 40cm: A = pi×r^2,
A = (40×40)pi = 1600pi = 5,026.55 cm^2.

So you can see that the [2-dimensional] area of this circle is 20 times the [1-dimensional] circumference

The answer is: a = about 63.59ft2 for 15