Find the area of the following circle. (Round answer to the nearest whole number).?

Question

Circumference = 280 cm. (Hint: Find r from C = 2r (round r to tenths); then find area

area =__?__cm

Answer 1

andyg77 is correct.  The first two are incorrect.  The more precise answer is 6238.8588 if  pi = 3.1416.

Answer 2

The diameter of a circle is equal to the circumference divided by pi

so d = c/pi = 280/3.14159 = 89.127

The radius is equal to the diameter divied by 2

so  r = d/2 = 89.127/2 = 44.56

and finally the area of a circle is equal to the radius squared times pi

A = pi*r^2 = 3.14159 * (44.56)^2 = 6237.92  <---Answer

Answer 3

c=2r

(please note circumference of a circle = pie * diameter or pie *2*radius) I am not sure you wrote this wrong.

₪₪₪₪₪ if this is true like you said in additional comments then the below answer is correct. The other people have used c=(pie)2r . To get the diameter  use the equation c=2r

2 time the radius is the diameter. so c=2r=280cm. This doesn't make sense but if that is the equation you were given then it is correct.

area =pie  r^2

pie =3.142

so c/2=r from the first equation

area = pie*(280 cm)/2)^2  = pie (280/2)*(280/2)=61583.2=61583 cm^2

or to simplify the radius is half the diameter and since we know the diameter is 280 cm half of that is 140 cm which would be the radius.

area =pie  r^2=pie(140cm)^2=61583 cm^2

Answer 4

C=2pi * r

280=6.28 * r

44.59=r

A=pi * r^2

A=pi *1988.27

A=6788.0 cm^2