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Two taps running together can fill a tank in  3\frac{1}{13}  hours. If one tap takes 3 hours more than the other to fill the tank, then how much time will each tap take to fill the tank ?

 

 

 

 
 
 
 
 

Answers (1)

Let the volume of the tank be  V\;m^3

Both taps A and B take  3\frac{1}{13}  hours to fill V\; m^3.

Let tap A fill at  V_A\; m^3/hr

And tap B fill at  V_B\; m^3/hr

Time taken by tap A to fill the tank =x\; hr

Time taken by tap B to fill the tank =(x+3)\; hr

According to question :

\left ( V_A+V_B \right )\times \left ( 3\frac{1}{13} \right )=V\; \; \; -(i)

V_A\times x=V\; \; \; -(ii)

V_B\times (x+3)=V\; \; \; -(iii)

From eq (ii)   \Rightarrow V_A=\frac{V}{x}

From eq (ii)  \Rightarrow V_B=\frac{V}{x+3}

Putting value of  V_A  and  V_B  in eq  (i) 

\left ( \frac{V}{x}+\frac{V}{x+3} \right )\times 3\frac{1}{13}=V

V\left ( \frac{1}{x}+\frac{1}{x+3} \right )\times \frac{40}{13}=V

\left ( \frac{x+3+x}{x(x+3)} \right )\times \frac{40}{13}=1          (cancelling V on both sides)

(2x+3)\times 40=13[x^2+3x]

80x+120=13x^2+39x

\Rightarrow 13x^2+39x-80x-120=0

\Rightarrow 13x^2-41x-120=0

\Rightarrow x=\frac{+41\pm \sqrt{(41)^2-4\times 13\times (-120)}}{2\times 13}

\Rightarrow x=\frac{41\pm \sqrt{1681+6240}}{26}

\Rightarrow x=\frac{41\pm \sqrt{7921}}{26}

\Rightarrow x=\frac{41\pm 89}{26}

\Rightarrow x=\frac{41+ 89}{26},\frac{41-89}{26}

\Rightarrow x=5,\frac{-24}{13}

Since x cannot be negative, hence x=5  hours.

Time taken by tap A to fill the tank =x=5 \; hour\!s

Time taken by tap B to fill the tank =x+3=8 \; hour\!s

 

 

Posted by

Ravindra Pindel

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