A can contains 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?	Choices
A) 10	B) 20	C) 21	D) 25	E) 26
Suppose the can initially contains 7x and 5x litres of mixtures A and B respectively   Quantity of A in mixture left   = (7x - 7/12 x 9) litres = (7x - 21/4) litres.   Quantity of B in mixture left   = (5x - 5/12 x 9) litres = (5x - 15/4) litres.   (7x - 21/4) / [(5x - 15/4)+9] = 7/9 = › 28x - 21/20x + 21 = 7/9 =› 252x - 189 = 140x + 147   =› 112x = 336 =’ x = 3.   So, the can contained 21 litres of A.   Answer 21
<result>C</result>
A can contains 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?