Question 773471
If the radius of a circle is decreased by 2 meters, the area of the circle is decreased by 80 pie m squared. what is the radius of the original circle?
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let r=radius of original circle
r-2=radius of circle decreased by 2 meters
area of circle=π*radius^2
...
πr^2-π(r-2)^2=80π
π cancels out
r^2-(r^2-4r+4)=80
r^2-r^2+4r-4=80
4r=84
r=21
radius of the original circle=21 meters