NIFT UG 2018 Question Paper with solutions

Question : 2 of 150

Marks: +1, -0

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?

Solution:

Let the original quantity be

12 x

L.
In

9 {L}

of the mixture
Liquid

A=\;{7}/{12} × 9=\;{21}/{4} {L}

Liquid

B=\;{5}/{12} × 9=\;{15}/{4} {L}

According to the question,

\;{7 x-{21}/{4}}/{5 x-\;{15}/{4}+9}=\;{7}/{9}

⇒ \;\; \;{28 x-21}/{20 x-15+36}=\;{7}/{9}

⇒ \;\; \;{28 x-21}/{20 x+21}=\;{7}/{9}

⇒ \;\; \;{4 x-3}/{20 x+21}=\;{1}/{9}

⇒36 x-27=20 x+21

⇒ 16 x=48

∴\;x =3

Original quantity of liquid

A

=7 x=7 × 3=21 {L}

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