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A can contains a mixture of 2 liquids A and B in proportion 7 : 5 when 9 liters of mixture are drawn off and the can is filled with B, the proportion of A and B becomes 7 : 9. How many liters of liquid A was contained by the can initially ?
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- 25
- 10
- 20
- 21
Correct Option: D
Let the can initially contain 7y litres and 5y litre of mixtures A and B respectively. Thus out of 12y litre of total mixture, 9 litre were taken out.
| Quantity of A in mix. left = |  | 7y - | × 7y |  | | | litres | 12x | 4 |
| Quantity of B in mix. left = | | 5y - | × 5y | | 12x |
| Quantity of B in mix. left = | | | litres | 4 |
| ∴ | | : | + 9 | | :: ( 7 : 9 ) | 4 | 4 |
Hence , Required answer 7y = 7 x 3 = 21 litre.
