Question

What is the area of a circle whose circumference is pie?

Answer 1

(A) pie/4
(B) pie/2
(C) pie
(D) 2pie
(E )4pie

Answer 2

Do you know what the formula for the circumference of a circle is?

Answer 3

yes. It's c=2pier

Answer 4

correct, so just equate that equation with \(\pi\) and work out what r is.
then use that to work out the area of the circle.

Answer 5

\[c=2\pi r\]

Answer 6

okay

Answer 7

let me know what value you get for r

Answer 8

pie/2pie

Answer 9

so the pie cancels out right?

Answer 10

yes

Answer 11

so r=2?

Answer 12

not quite - pay attention to the fraction that you have:\[r=\frac{\pi}{2\pi}\]

Answer 13

yes i have that right now

Answer 14

so area = ?

Answer 15

do i keep it like that?

Answer 16

hold on a second

Answer 17

no - you need to cancel the \(\pi\)'s in the expression for r

Answer 18

okay

Answer 19

\[r=\frac{\pi}{2\pi}=\frac{\cancel{\pi}}{2\cancel{\pi}}=?\]

Answer 20

2? or 1/2?

Answer 21

which one do you think it is?

Answer 22

1/2?

Answer 23

perfect!

Answer 24

yay :)

Answer 25

so now just calc the area

Answer 26

okay

Answer 27

i got pie times 1/4 which is same thing as answer choice A, pie divded by 4

Answer 28

yes - well done! :)

Answer 29

:) thank you so much!

Answer 30

yw :)