InterviewSolution
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Two water pipes together can fill a tank in9/3/8 the pipe of larger diameter takes 10 hours less than the smaller one to fill the tank separately find the time in which each pipe can fill the tank separately |
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Answer» Answer: Answer: Let the tap with SMALLER diameter fills the tank alone in X HOURS Let the tap with larger diameter fills the tank alone in (x – 10) hours. In 1 hour, the tap with a smaller diameter can FILL 1/x part of the tank. In 1 hour, the tap with larger diameter can fill 1/(x – 10) part of the tank. The tank is filled up in 75/8 hours. Thus, in 1 hour the taps fill 8/75 part of the tank. 1/x + 1/(x-10) = 8/75 (x-10) + x / x(x-10) = 8/75 2x – 10/x(x-10) = 8/75 75 (2x-10) = 8(x2-10x) by cross multiplication 150x – 750 = 8x2 – 80x 8x2 − 230x + 750 = 0 4x2−115x + 375 = 0 4x2 − 100x −15x + 375 = 0 4x(x−25)−15(x−25) = 0 (4x−15)(x−25) = 0 4x−15 = 0 or x – 25 = 0 x = 15/4 or x = 25 Case 1: When x = 15/4 Then x – 10 = 15/4 – 10 ⇒ 15-40/4 ⇒ -25/4 Time can never be negative, so x = 15/4 is not possible. Case 2: When x = 25 then x – 10 = 25 – 10 = 15 ∴ The tap of smaller diameter can separately fill the tank in 25 hours, and the time taken by the larger tap to fill the tank = (25 – 10) = 15 hours.
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