A water tank has one inlet, A and one outlet, B. A takes 5 hours to fill the empty tank, when B is not open and B takes 8 hours to empty the full tank, if the tank  is three fifth full, how much time will it take to fill the tank completely when both A and B are opened simultaneously ?(in hours)

In a village, 30% of the villagers belong to upper economic class. The number of villagers who belong to middle economic class are 3/2  of the number of villagers who belong to lower economic class. If 6860 villagers belong to lower economic class, what is the population of the village ?

Boat A travels upstream from point X to point Y in 2 hours more than the time taken by Boat B to travel downstream from point Z to point Y. The distance between X and Y is 40 km and the distance between Y and Z is 24km. The speed of Boat A in still water is equal to the speed of Boat B downstream. What is the speed of Boat A in still water ? (Consider the speed of the current to be the same.)

Which of the given countries has the highest number of average employees per office ?

What is the difference between the average number of post-graduate employees in countries A,B and D together and the average number of Post-graduate employees in countries F,G and H together ?

What is the respective ratio between total number of male employees in countries B and H together and total number of female employees in countries C and D together?