A chemical supply company has 60 liters of a 20% HNO3 solution. How many liters of pure undiluted HNO3 must the chemists add so that the resultant solution is a 50% solution?	Choose the correct choice from the following choices:	A) 12	B) 15	C) 20	D) 24	E) 36

Rationale: "60 liters of a 20 % hno 3 solution means hno 3 = 12 liters in 60 liters of the solution . now , let x be the pure hno 3 added . as per question , 12 + x = 50 % of ( 60 + x ) or x = 36 . hence , e"
Answer: E