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?
After giving three successive discounts of 15%, 5% and p%, respectively, on the marked price of an article of Rs. 4,800, It is sold for Rs. 3,100.80. What is the value of p?