Several litres of acid were drawn offa 54 litre vessel full of acid and an equal amount of water was added. Again the same volume of the mixture was drawn off and replaced by water. As a result, the vessel contained 24 litres of pure acid. How much of the acid was drawn off initially? Choose the correct choice from the following:	A) 12 lts	B) 16 lts	C) 18 lts	D) 24 lts	E) 28 lts
Suppose X litres of acid was drawn off initially.   Remaining acid in the 54 litre vessel full of acid.   =&gt; (54 - x) litres and water added = x litres.   Now out of the 54 litres of mixture of acid and water x litres of mixture is drawn off.   =&gt; quantity of acid drawn off =(54 - X/54 x X)   litres and quantity of water drawn off = X2/54   Now vessel contains [54 - X - (54 - X/54)X]   Thus, 54 - X - [54 - X/54]X = 24   =&gt; X2 - 108X +1620 = 0   =&gt; X = 80, 18   since 90 &gt; 54 therefore X = 90 is ruled out   hence X = 18   ANSWER:18 lts
<result>C</result>
Several litres of acid were drawn offa 54 litre vessel full of acid and an equal amount of water was added. Again the same volume of the mixture was drawn off and replaced by water. As a result, the vessel contained 24 litres of pure acid. How much of the acid was drawn off initially?