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  1. 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. Litres of liquid A
    contained by the can initially was
    1. 10
    2. 20
    3. 21
    4. 25
Correct Option: C

Let A = 7x litre, B = 5x litre
In 9 litres of mixture,

A =
7x
× 9 =
21
litres
12x4

B =
5x
× 9 =
15
litres
12x4

In new situation,
7x −
21
= 7/9
4
5x −
15
+ 9
4

⇒ 
28x − 21
=
7
20x − 15 + 369

⇒  252x – 189 = 140x + 147
⇒  112x = 336 ⇒ x = 3
∴  Initial quantity of liquid A
= 7x = 7 × 3 = 21 litres



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