Area of circle = (∏r^2)/2
substitute the area to the formula u will get the radius of 25cm which is the width of the rectangle and when u double it which is 50 that is the length of the rectangle b'coz it is coincides so the diameter of the circle is lie on the length of the when u get the area of the rectangle just simply multiply width of 25 and length of 50. you will get the area wch is 1250
it is not the formula of a circle.. it is semicircle..