A tub can be filled with hot water in 15 minutes, or with cold water in 12 minutes. The tub can also be emptied when the plug is pulled out, in 10 minutes. Farley ran the hot water in his tub for 6 minutes, then both the cold and hot water together for 3 minutes, and then with the two taps still running, he accidentally pulled the plug. How long did it take, in minutes, for the tub to fill after the plug was pulled?
Tub capacity = 100 L Hot water = H Cold water = C
H => 6 min = 40 L
H + C => 3 min = 20 L + 25 L
At this point, the tub is 85% filled with water.
In one minute: H = 62/3 L, C = 81/3 L, D = 10 L (D - drain)
Hence, it will take 3 minutes for the tub to be filled.