Banking Quantitative Aptitude Sample Paper Quantitative Aptitude Sample Paper-43

A can contains a mixture of two liquids A and B in the ratio 7: 5.When 9 L of mixture are drained 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?

A) 10

B) 20

C) 21

D) 25

Correct Answer: C

Solution :

Let the original quantity be \[12x\,\,L\]

In \[9\,\,L\]of the mixture,

Liquid \[A=\frac{7}{12}\times 9=\frac{21}{4}\,\,L\]

Liquid \[B=\frac{5}{12}\times 9=\frac{15}{4}\,\,L\]

According to the question,

\[\frac{7x-\frac{21}{4}}{5x-\frac{15}{4}+9}=\frac{7}{9}\]\[\Rightarrow \]\[\frac{28x-21}{20x-15+36}=\frac{7}{9}\]

\[\Rightarrow \] \[\frac{28x-21}{20x+21}=\frac{7}{9}\]\[\Rightarrow \]\[\frac{4x-3}{20x+21}=\frac{1}{9}\]

\[\therefore \] \[x=3\]

Original quantity of liquid \[A=7x=7\times 3=21\,\,L\]