A can contains a mixture of liquids A and B is the ratio 7:5. When 15 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 the most appropriate option.
A) 30  B) 35  C) 40  D) 45  E) 50
Ci*Vi = Cf*Vf   (7/12)*(V1 - 15) = (7/16)*V1   (V1 - 15)/V1 = 3/4   15 accounts for the difference of 1 on ratio scale so Initial volume = V1 = 4*15= 
<gadget id="calculator">4*15</gadget>
<output>60</output>
60 litres.   7/12 of the initial mixture was liquid A so liquid A was   (7/12)*60= 
<gadget id="calculator">  (7/12)*60</gadget>
<output>35</output>
35 litres.   Answer : 35
<result>B</result>
A can contains a mixture of liquids A and B is the ratio 7:5. When 15 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?