Question

Two concentric circles with centre 0 and radius r and r respectively.if r=3r,express the area ofthe shaded part in terms of Pie and r

Answer 1

So much wrong with this post.

You have 2 circles with the same centre and "radius r and r" , makes
no sense.
then: "if r=3r" ???? , not possible unless r = 0. That's like saying 5 = 15
then: Pie !! Is that an apple or a blueberry pie. You meant pi or π

Anyway, my interpretation of that gibberish is that you have 2
circles with the same centre and the larger circle has a radius which
is three times that of the smaller.

Area of larger circle = 9πr^2
area of smaller circle = πr^2

Depending on what is shaded, you don't say, do the appropriate
calculation. My guess would be that you want 8πr^2, the "ring" formed
by the larger and the smaller circles.