Six pipes are fitted to a water tank. Some of these are inlet pipes and the others outlet pipes. Each inlet pipe can fill the tank in 9 hours and each outlet pipe can empty the tank in 6 hours. On openingall the pipes, an empty tank is filled in 9 hours. The number of inlet pipes is .......
Let number of inlet pipes be $$x$$ and number of outlet pipes = $$(6-x)$$
According to ques,
=> $$\frac{x}{9}-\frac{(6-x)}{6}=\frac{1}{9}$$
=> $$\frac{6x-54+9x}{54}=\frac{1}{9}$$
=> $$15x-54=6$$
=> $$15x=60$$
=> $$x=\frac{60}{15}=4$$
$$\therefore$$ There are 4 inlet pipes.
=> Ans - (A)