A set of 10 pipes (set X) can fill 70% of a tank in 7 minutes. Another...
Solution:
Given,
- Set X of 10 pipes can fill 70% of the tank in 7 minutes.
- Set Y of 5 pipes fills 3/8 of the tank in 3 minutes.
- Set Z of 8 pipes can empty 5/10 of the tank in 10 minutes.
Let's assume that the tank has a capacity of 100 units.
- So, Set X can fill 70 units of the tank in 7 minutes, i.e., (70/7) units/minute.
- Set Y can fill (3/8)*100 = 37.5 units of the tank in 3 minutes, i.e., (37.5/3) units/minute.
- Set Z can empty (5/10)*100 = 50 units of the tank in 10 minutes, i.e., (5/10) units/minute.
To find out the time taken to fill the tank if all the 23 pipes are opened at the same time, we need to calculate the net flow rate of water in the tank.
Let's denote the net flow rate by F.
- F = (flow rate of water coming in) - (flow rate of water going out).
- Flow rate of water coming in = (flow rate of Set X) + (flow rate of Set Y).
- Flow rate of water going out = (flow rate of Set Z).
So,
- Flow rate of Set X = (70/7) units/minute = 10 units/minute.
- Flow rate of Set Y = (37.5/3) units/minute = 12.5 units/minute.
- Flow rate of Set Z = (5/10) units/minute = -0.5 units/minute (negative sign indicates water is going out of the tank).
Therefore,
- F = (10 + 12.5) - (-0.5) = 23 units/minute.
To fill the tank completely, we need to add 100 units of water. So, the time taken to fill the tank completely is given by:
- Time taken = (100/23) minutes = 4.34 minutes (approx).
Therefore, the correct answer is option (a) 5 minutes.
Note:
- It is important to convert all the given information into a common unit (units/minute, in this case) to calculate the net flow rate.
- The negative sign in the flow rate of Set Z indicates that water is going out of the tank, i.e., Set Z is emptying the tank.
A set of 10 pipes (set X) can fill 70% of a tank in 7 minutes. Another...
B
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