A chemical supply company has 60 liters of a 45% HNO3 solution. How many liters of pure undiluted HNO3 must the chemists add so that the resultant solution is a 50% solution?  Choose one:
A) 6
B) 15
C) 20
D) 24
E) 30

Rationale: "60 liters of a 45 % hno 3 solution means hno 3 = 27 liters in 60 liters of the solution . now , let x be the pure hno 3 added . as per question , 27 + x = 50 % of ( 60 + x ) or x = 6 . hence , a"
Answer: A