Description for Correct answer:
Let numbr of outlets be x.

Therefore, Number of inlets = \( \Large \left(7-x\right) \)

Timer taken to fill the tank when all the pipes are opened = \( \Large \frac{30}{11}h \)

Part of tank filled in 1 h when all the pipes are opened = \( \Large \frac{11}{30}h \)

According to the question,

\( \Large \frac{7-x}{10}-\frac{x}{15}=\frac{11}{30} \)

=> \( \Large \frac{3 \left(7-x\right)-2x}{30}=\frac{11}{30} \)

=> 21 - 3x - 2x = 11

=> 5x = 10

Therefore, x = 2

Hence, number of outlets = 2

and number of inlets = 7 - 2 = 5