1) Three pipes X, Y and Z can fill a tank from empty to full in 30 minutes, 20 minutes, and 10 minutes respectively. When the tank is empty, all the three pipes are opened. X, Y and Z discharge chemical solutions A,B and C respectively. What is the proportion of the solution C in the liquid in the tank after 3 minutes?
Answer:D) 3 hours 45 mins
Half tank will be filled in 3 hours Lets calculate remaining half,
3) A water tank is two-fifth full. Pipe A can fill a tank in 12 minutes and pipe B can empty it in 6 minutes. If both the pipes are open, how long will it take to empty or fill the tank completely?
A) 2.8 min
B) 4.2 min
C) 4.8 min
D) 5.6 min
Answer:C) 4.8 min
Let B be turned off after x minutes. Then,
Part filled by (A + B) in x min. + Part filled by A in (30 -x) min. = 1.