Pipes and Cisterns Practice Test 2 with solutions

Question : 29 of 40

Marks: +1, -0

Three pipes A, B and C attached to a cistern can fill it in 12, 20 and 24 hours respectively. At first, all the three pipes are opened simultaneously. After 2 hours, Pipe C is closed and after further 2 hours, Pipe B is closed. Pipe A is kept open till the cistern gets completely filled. What fraction of tank is filled by Pipe ‘A’?

${57}/{60}$
${37}/{60}$
${41}/{60}$
${43}/{60}$
${23}/{60}$

Validate

Solution:

Part of cistern filled by Pipes A, B and C together in 2 hours =

(1/{12}+1/{20}+1/{24}) × 2

2 × ({10+6+5}/{120})

{21×2}/{120}

7/{20}

Part of cistern that remains empty = 1 -

7/{20}

{13}/{20}

Part of cistern filled by A and B in 2 hours
=

(1/{12}+1/{20}) × 2

({5+3}/{60}) × 2

{8×2}/{60}

4/{15}

Part of cistern that remains empty
=

{13}/{20}-4/{15}

{39-16}/{60}

{23}/{60}

Fraction of cistern filled by A alone
= $4 × 1/{12}+{23}/{60}4
=

1/3 + {23}/{60}

{20+30}/{60}

{43}/{60}

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