A can contains a mixture of liquids A and B is the ratio 7:5. When 12 litres of mixture are drawn off and the can is filled with B, the ratio of A and B becomes 7:9. How many liter of liquid A was contained by the can initially? Choose one.
A) 25  B) 27  C) 29  D) 28  E) 31
Ci*Vi = Cf*Vf   (7/12)*(V1 - 12) = (7/16)*V1   (V1 - 12)/V1 = 3/4   12 accounts for the difference of 1 on ratio scale so Initial volume = V1 = 4*12= 
<gadget id="calculator">4*12</gadget>
<output>48</output>
48 litres.   7/12 of the initial mixture was liquid A so liquid A was   (7/12)*48= 
<gadget id="calculator">  (7/12)*48</gadget>
<output>28</output>
28 litres.   Answer : 28
<result>D</result>
A can contains a mixture of liquids A and B is the ratio 7:5. When 12 litres of mixture are drawn off and the can is filled with B, the ratio of A and B becomes 7:9. How many liter of liquid A was contained by the can initially?