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# Two pipes can fill a tank in 20 and 24 minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in 15 minutes. The capacity of the tank is:

A. 60 gallons

B. 100 gallons

C. 120 gallons

D. 180 gallons

E. None of these

### Solution(By Examveda Team)

Work done by the waste pipe in 1 minute
\eqalign{ & = \frac{1}{{15}} - \left( {\frac{1}{{20}} + \frac{1}{{24}}} \right) \cr & = {\frac{1}{{15}} - \frac{{11}}{{120}}} \cr & = - \frac{1}{{40}}\,\,\,\,\,\left[ { - ve\,{\text{sign}}\,{\text{means}}\,{\text{emptying}}} \right] \cr & \therefore {\text{Volume}}\,{\text{of}}\,\frac{1}{{40}}{\text{part}} = 3\,{\text{gallons}} \cr & {\text{Volume}}\,{\text{of}}\,{\text{whole}} \cr & = \left( {3 \times 40} \right){\text{gallons}} \cr & = 120\,{\text{gallons}} \cr}

This Question Belongs to Arithmetic Ability >> Pipes And Cistern

1. Let, capacity is x gallon
(X/20+X/24)*15= 11x/8

Now,11x/8-x=15*3
3x/8=45
X= 120

2. Add up the work of two pipes i.e. 11/120. Let total work is x then work done by these two pipes in one minute is 11x/110. Now, equation will be
(11x/110)-3=x/15

3. I didn't understand this plz explain

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