Two taps P and Q can fill a tank in 24 hours and 18 hours respectively. If the two taps are opened at 11 a.m., then at what time (in p.m.) should the tap P be closed to completely fill the tank at exactly 2 a.m.?
In a row of boys, Amit is ranked 12th from top and Ratan is 15th from bottom. They interchange their position. Ratan now becomes 37th from bottom. How many total boys are there in the row?