A can contains a mixture of liquids A and B is the ratio 7:5. When 18 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 correct choice from the following answers.
A) 32
B) 52
C) 62
D) 42
E) 48
Ci*Vi = Cf*Vf   (7/12)*(V1 - 18) = (7/16)*V1   (V1 - 18)/V1 = 3/4   18 accounts for the difference of 1 on ratio scale so Initial volume = V1 = 4*18= 
<gadget id="calculator">4*18</gadget>
<output>72</output>
72 litres.   7/12 of the initial mixture was liquid A so liquid A was   (7/12)*72= 
<gadget id="calculator">  (7/12)*72</gadget>
<output>42</output>
42 litres.   Answer : 42
<result>D</result>
A can contains a mixture of liquids A and B is the ratio 7:5. When 18 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?