A container 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 4 times. Find how much spirit is left in the resulting mixture finally? Choose the correct choice from the following:
A) 8(257/525) gallons
B) 8(346/625) gallons
C) 8.192 gallons
D) 8.25 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)^4 / 20^4   Left QTY = 20 (16/20)^4   Left QTY = 20 ( 4/5 )^4   Left QTY = 8.192   Answer is 8.192 gallons
<result>C</result>
A container 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 4 times. Find how much spirit is left in the resulting mixture finally?