Two pipes can fill a tank in 15 hours and 4 hours, respectively, while a third pipe can empty it in 12 hours. How long (in hours) will it take to fill the empty tank if all the three pipes are opened simultaneously?
Answer & explanation
Correct answer: option 3
A+ = 15 hrs, B+ = 4 hrs, C- = 12 hrs,
⇒ Time required by A + B + C to fill the tank completely = \(\frac{60}{4+15-5}\) = \(\frac{60}{14}\) = \(\frac{30}{7}\) hrs.