中三數一問

Let y be the original area.

{[3.14x(1.1y)^2]-(3.14y^2)/3.14y^2}x100%
=3.14x1.21y^2-3.14y^2/3.14y^2x100%
=3.7994y^2-3.14y^2/3.14y^2x100%
=0.6594y^2/3.14y^2x100%
=0.21x100%
=21%
The % cange is 21%

2007-09-09 13:21:23 補充：
The % change is 21%

21%!!!