For achieving self cleaning velocity, 150 mm dia pipe should have a slope of

54) What is the meaning of the word Plumbum?

55) The inlet valve of a water tank of capacity 18 m3 is set at a flow rate of 0.3 litres /sec. The time required to fill the tank is

56) The presence of lead in water can be detected by using

57) One unit of purified water is equivalent to