Question 1173910: What is the radius of a circle with an area of 144 pi?
The correct answer is 12 but I want to understand step by step of the formulas of how that is the correct answer please.
Found 2 solutions by Boreal, ikleyn:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! area is π*r^2
so 144π=π*r^2
divide by π both sides
144=r^2
take the square root of both sides
r=12
it's easier leaving it in π
but if you multiply by 3.14, the area is 452.16
if you divide that by 3.14, you get 144. It takes you right back to where you started.
Many times, you don't need to convert π to an estimate. Just leave it as π, and when you divide, it disappears.
Answer by ikleyn(52812)  (Show Source):
You can put this solution on YOUR website! .
For it, you need to know the formula for the area of a circle.
This formula is
the area =  .
where r is the circle's radius.
The students learn it for the first time, probably, in their 3rd grade, and their teacher explains them
that  is the number (a constant value), for which people use an approximate value 3.14.
So, for your problem, you get this equation
 = (*)
Next in equation (*), you divide both sides by this constant value , and you get then
144 =  .
Finally, you take the square root from both sides, and - - - o-o-o-p (!) - - - you get
r =  = 12.
Thus you get your final answer (!)
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Is everything clear to you in my explanation ?
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