Railways Sample Paper RRB (Group D) Sample Test Paper-2

  • question_answer
    Two inlet pipes can fill a cistern in 10 and 12 hours respectively and an outlet pipe can empty 80 gallons of water per hour. All the three pipes working together can fill the empty cistern in 20 hours. What is the capacity (in gallons) of the tank?

    A)  360                 

    B)              300

    C)  600                 

    D)  900

    Correct Answer: C

    Solution :

    [c] Part filled by first pipe in 1 hour \[=\frac{1}{10}\] Part filled by second pipe in 1 hour \[=\frac{1}{12}\] Suppose the waste pipe can empty the full tank in x hours. Then, part emptied by waste pipe in 1 hour \[=\frac{1}{x}\] All the three pipes can fill the tank in 20 hours I.e. part filled by all three pipes in hour \[=\frac{1}{20}\] Now, \[\Rightarrow \,\,\,\frac{1}{10}+\frac{1}{12}-\,\frac{1}{x}=\frac{1}{20}\] \[\Rightarrow \,\,\,\frac{1}{x}=\frac{1}{10}+\frac{1}{12}-\,\frac{1}{20}=\frac{8}{60}=\frac{2}{15}\] \[\therefore \,\,\,x=\frac{15}{2}\] i.e, the waste pipe can empty the full tank in\[\frac{15}{2}\]hour Given that the waste pipe can empty 80 gallons per hour. Therefore, in \[\frac{15}{2}\] hours, it can empty \[\frac{15}{2}\times 80=600\]gallons. .Hence, volume of the tank = 600 gallons.


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