Simple math help?

Question

What is the circumference of a circle with a diameter of 4?
What is the area of a circle with a diameter of 4?

Answer 1

Circumference is 4 times pi, approx 12.56

Area is pi * radius squared or about pi * 4, approx 12.56

Answer 2

Ratio of circumference to diameter is pi. If the circle has a diameter of 4, the circumference is 4 pi.

Area of a circle is the RADIUS squared times pi (the old "pi r squared" thing.) The radius is 1/2 the diameter. For a diameter of 4, the radius is 2. 2 squared is 4, so the area is 4 pi.

Your math teacher was being cute by giving you the one example where the circumference is the same as the area, though the circumference is in linear units (inches, meters, etc.) and the area is in square units of area (square inches, square centimeters, etc.)

Answer 3

What is the circumference of a circle with a diameter of 4?
c = πd (3.142 x 4) = 12.568

What is the area of a circle with a diameter of 4?
a = πrsquared (3.142 x 2 x 2) = 12.568

The same !

Answer 4

circumference = pi x diameter -or- 2 x pi x radius

area = pi x r^2

so circumference would be 12.5663

and area would be 12.5663 in^2

Answer 5

simply the circumference of a circle = πd = 2πr
= 3.14*4=12.56 cm

but area of a circle= πr^2=3.14*2^2=12.56 cm^2

Answer 6

don't u have a formula for this?
something like C=d... and something with pi
same thing for the area....
but for the area you'll need to use r=2 (half the diameter)

Answer 7

d=4 so r=2
p=2*pi*r=4 pi = 4*3.14
A= pi*r*r= 4 pi = 4*3.14

Answer 8

r=2
pi*r*2
pi*2*2= 12.566

area
r=2
pi*r^2
pi*2^2 = 12.566