A square mirror has exactly half the area of the rectangular wall on which it is hung. If each side of the mirror is 18 inches and the width of the wall is 32 inches, what is the length of the wall, in inches?  Choices:
A) 15.25
B) 18.25
C) 19.25
D) 20.25
E) 21.25

Rationale: "since the mirror is 42 inches in all sides , it must be a square . area of a square is a = a ^ 2 ; 18 ^ 2 = 324 . area of rectangle is double of that 2 * 324 = 648 . now a = lw and we need find w so a / l = w ; 648 / 32 = 20.25 answer ! answer is d"
Answer: D