A tank has a capacity of 20 gallons and is full of spirit. 4 gallons of spirit is drawn out and the container is again filled with water. This process is repeated 5 times. Find how much spirit is left in the resulting mixture finally?
Pick one
A) 6(257/525) gallons  B) 20(346/625) gallons  C) 6.5 gallons  D) 6.25 gallons  E) None of these
There is a direct formula to calculate such repetition:   Left QTY / Orig QTY = ( (Orig QTY - Rep QTY) / Orig QTY )^n   where n is number of times mixing done:   Left QTY / 20 = (20 -4)^5 / 20^5   Left QTY = 20 (16/20)^5   Left QTY = 20 ( 4/5 )^5   Left QTY = 20(346/625)   Answer is 20(346/625) gallons
<result>B</result>
A tank has a capacity of 20 gallons and is full of spirit. 4 gallons of spirit is drawn out and the container is again filled with water. This process is repeated 5 times. Find how much spirit is left in the resulting mixture finally?