If the area of a circle decreases by 20%, then the radius of a circle decreases by
Pick one:
A) 20 %	B) 18 %	C) 36 %	D) 11 %	E) none of these

Rationale: if area of a circle decreased by x % then the radius of a circle decreases by ( 100 − 10 √ 100 − x ) % = ( 100 − 10 √ 100 − 20 ) % = ( 100 − 10 √ 80 ) % = 100 - 89 = 11 % answer d
Answer: D