TITLE: What is wrong with this circle's area problem?
QUESTION [6 upvotes]: My solution and my book's solution don't match.
Is something wrong with the my solution?
If so, where and why?
My book says:

The radius r of a circle increases by 50%.
  In terms of r, what is the area of the circle 
  with the increased radius?

My solution:

A = $\pi r^2\ $ => Area of any circle
ir = $\ 3r/2 \ $ => Increased radio
A$\ _{ir}  = \pi ir^{2}  \ $ => Area of circle with increased radio
A$\ _{ir}  = \pi (3r/2 )^{2}  \ $ => Substituting ir with its value
A$\ _{ir}  = \pi (9r^2/4 )  \ $ => Square
A$\ _{ir}  = \ (9\pi r^2 )/4   \ $ => Result

Is the In terms of r tricky?

REPLY [3 votes]: There is nothing wrong with your answer!