In 5 hours and 10 hours, respectively. It can be emptied bycistern be filled up completely?third tap C in 20 hours. If all the taps are turned on at the same time, in how much time will the emp17. A pipe can fill a cistern in 6 hours. Due to a leak in the bottom, it is filled in 7 hours. When the cisteriS.full, in how much time will it be emptied by the leak?If 25 girls earn 3,000 in 15 days, how much will 35 girls earn in 18 days?p can do a piece of work in 15 days. P and R can do it in 10 days and P, Q and R in 6 days. In howdays can P and Q together do it?Now You Know...Two quantities are said to be in direct proportion (or direct variation) if with the increase or decreof one quantity, the other quantity also increases (or decreases).If x and y are in direct proportion, then - = k (k is any constant). The constant kis called the conof variation.y уTwo quantities are said to be in inverse proportion (or inverse variation) if with the in(or decrease) of one quantity, the other quantity decreases (or increases).​