SOLUTION: This problem includes "Pie"=3.14. I can't find a way to symbolize "pie". I hope this doesn't affect your ability to help. Also this is part of factoring polynomials. "The sum of

Question 739949: This problem includes "Pie"=3.14. I can't find a way to symbolize "pie". I hope this doesn't affect your ability to help. Also this is part of factoring polynomials.
"The sum of the areas of two circles is 169pie square inches. the length of a radius of the smaller circle is 7 inches less than the length of a radius of the larger circle. Find the length of the larger circle."
I am not sure how to set this problem up to solve it. I don't remember how to find the area of a circle.
Any step by step help would be appreciated. thank you!
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
"The sum of the areas of two circles is 169pie square inches. the length of a radius of the smaller circle is 7 inches less than the length of a radius of the larger circle. Find the length of a radius of the larger circle."
***
area of a circle=πr^2
let r=radius of larger circle
area of larger circle=πr^2
r-7=radius of smaller circle
area of smaller circle=π(r-7)^2
sum of the areas of two circles is 169pie square inches
πr^2+π(r-7)^2=169π
factor out π
r^2+(r-7)^2=169
r^2+r^2-14r+49=169
2r^2-14r-120=0
r^2-7r-60=0
(r+5)(r-12)=0
r=-5 (reject, r>0)
or
r=12
r-7=5
radius of larger circle=12 sq in
radius of smaller circle=5 sq in
RELATED QUESTIONS
Can someone show me this please and show a diagram please and thanks.Let P(t)be the point (answered by stanbon)

C=2(pie)r for r..i dont understand how to solve this. i would like some help exlaining... (answered by Fombitz)

I have been trying to solve this for days and could really use some help. Will you take... (answered by Nate)

Hello, I could use some help on this problem: A circle is shrinking in size, and... (answered by stanbon)

OK, I need to find out why 3 divided by 4 + Pie/ 2Pie is supposed to be equal to 2/3.... (answered by Fermat,Alan3354)

A diagram is needed please i need to understand this .I am having a hard time. 1.)If... (answered by KMST)

Pls. Help!!! I can't understand this lesson. It's called Formula Manipulation The... (answered by Alan3354)

Plug in and solve to the best of your ability T = 2╦√L/32 T=2.2... (answered by Alan3354)

Hi there! I have never solved a problem like this before so I am not sure how to start.... (answered by Alan3354)