A water tank has inlets of two types A and B. All inlets of type A when open, bring in water at the same rate. All inlets of type B, when open, bring in water at the same rate. The empty tank is completely filled in 30 minutes if 10 inlets of type A and 45 inlets of type B are open, and in 1 hour if 8 inlets of type A and 18 inlets of type B are open. In how many minutes will the empty tank get completely filled if 7 inlets of type A and 27 inlets of type B are open?
Started 4 months ago by Shashank in
Explanatory Answer
Let A be the rate at which pipe A fills the tank in one minute and B be the rate at which pipe B fills
in one minute
From the question, we can infer that 10A + 45B = 1/30 (Since it takes 30 minutes to fill, 1/30 th o
f the tank gets filled in 1 minute)
Similarly, we can also infer that 8A + 18B = 1/60
On simplifying, we get
2A + 9B = 1/150 ---(1)
4A + 9B = 1/120 ---(2)
Solving both, we get
2A = 1/120 - 1/150
A = 1/1200
On substituting the value of A in the equation, we get B = 1180011800
So, 7A + 27B = 7 × 1/1200 + 27 × 1/1800 = (7+18)/1200 = 1/48 th of the tank in 1 minute
So, the pipes fill the tank in 48 minutes
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