Question

A tank is connected with 8 pipes. Some of them are inlet pipes and rest work as outlet pipes. Each of the inlet pipe can fill the tank in 8 hours, individually, while each of those that empty the tank i.e., outlet pipe, can empty it in 6 hours individually. If all the pipes are kept open when the tank is full, it will take exactly 6 hours for the tank to empty. How many of these are inlet pipes?

• A. 2
• B. 4
• C. 5
• D. 6

Answer 1

The correct option is B 4

Let there be 'n' inlet pipes then there must be (8-n) outlet pipes
Therefore $(8-n)\frac{1}{6}-n\times \frac{1}{8}=\frac{1}{6}\Rightarrow n=4$

Alternatively: $(8-n)16.66-n\times 12.5=16.66\Rightarrow n=\frac{116.66}{29.16}=\frac{700}{175}=4$

Alternatively: It can be solve through options very easily.