A can contain a mixture of two liquids A and B in the ratio 7:5 when 9 litres of mixture are drawn off and the can is filled with B, the ratio of A and B becomes 7:9. How many litres of liquid A was contained by the can initially?
Choose the correct choice from the following answers:
A) 28 litres
B) 21 litres
C) 45 litres
D) 36 litres
E) None of these
Explanation :   Let, the can initially contains 7x and 5x litres of mixtures A and B respectively.   When 9 litres of mixture are drawn off, quantity of A in mixture left :-   =&gt;7x−(7/12)×9=7x−(21/4) litres.   Similarly, quantity of B in mixture left:   =&gt;5x−(5/12)×9=5x−(15/4) litres.   The ratio becomes :   =&gt;(7x−21)/(5x−(15/4)+9)=7/9.   =&gt;(28x−21)/(20x+21)=7/9.   =&gt;252x−189=140x+147.   =&gt;112x=336.   =&gt;x=3.   Hence, the required initial amount of A is :   =&gt;7×x=7×3=21 litres.   Answer : 21 litres
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A can contain a mixture of two liquids A and B in the ratio 7:5 when 9 litres of mixture are drawn off and the can is filled with B, the ratio of A and B becomes 7:9. How many litres of liquid A was contained by the can initially?