Spidy001 wrote:
In the figure, small circel with radius r intersects larger circle with radius R (R>r). If k>0, what is the difference in the areas of the non overlapping parts of two circles?
(1) R=r+3k
(2) kR/(kr-6)=-1
Let x be the overlapping area.
we were asked find difference in non overlapping areas = \((pi*R^2-x)-(pi*r^2-x)\)
= pi*(R^2-r^2) = pi*(R+r)*(R-r)
1. Not sufficient.
we only know R-r ,not R+r.
2. Not sufficient
\(kR/(kr-6) = -1\)
=> R+r = 6/k. but we dont know R-r
Together, its sufficient.
= pi*(R+r)(R-r) = pi*(6/k)(3k) = 18pi.
Answer is C.
I have one question in the above explanation.
Shouldnt x be deducted only once in the equation ?? ..
(pi*R^2-x)-(pi*r^2-x) --> (pi*R^2)-(pi*r^2) - x
We are asked about the difference between the areas of green and yellow regions.
, so, as you can see we should subtract red region (x) from the areas of both circles.
.