Question

what is the radius of a circle with an area of 9 pi

Answer 1

2
pi
9
3
none of above

Answer 2

\[A=\pi r^2 \Rightarrow 9 \pi = \pi r^2\]
solve for r

Answer 3

i know that... i dont have r

Answer 4

yes, you're supposed to solve for r...
\(9\pi=\pi r^2\) divide both sides by \(\pi\) and then take the square root fo each side... what do you get?

Answer 5

i got .1444
9*3.14=3.14*r*r
9*3.14=28.26
28.26/2=14.13
r=14.13

Answer 6

\[9\pi = \pi r^2 \Rightarrow 9 = r^2 \Rightarrow r = 3\]

Answer 7

so 9*3.14 should = 3.14*r squared. the that is nine which equals r squared and r is 3

Answer 8

right?

Answer 9

@zaibali.qasmi
@ganeshie8
@mathmale (Moderator)

Answer 10

If you have a value for the radius, r, now, recall that the area of a circle is pi*(radius)^2.

Substitute your value for r. If the result is the same as you started with (9pi square units), then you know your answer (for the radius) is correct.

Answer 11

use this realtion

\[r=\sqrt{\frac{ A }{ \pi }}\]

put values and solve..

Answer 12

@zaibali.quasmi: Would you mind explaining to math-geek where this formula came from, and why you obtained it?

Answer 13

its fine

Answer 14

what if its like 4pi

Answer 15

well..

see

formula for area of circle is

A=pi * r^2
=> A/pi= r^2

=>r=sqrt A/pi

if you see the math geek coments carefully..he used this formula..

Answer 16

true...true