If the radius of a circle decreased by 50% its area is decreased by:  Choose the correct choice:
A) 75	B) 79	C) 72	D) 70	E) 80

Rationale: original area = π r ( power ) 2 new area = π ( r / 2 ) ( power ) 2 = ( π r ( power ) 2 ) / 4 reduction in area = [ ( π r ( power ) 2 - ( π r ( power ) 2 ) / 4 ] 2 = ( 3 π r ( power ) 2 ) / 4 reduction percent = ( ( 3 π r ( power ) 2 ) / 4 × 1 / ( π r ( power ) 2 × 100 ) % = 75 % answer is a .
Answer: A