In a three-layered soil, water flows parallel to stratification. The thickness of the middle layer is twice that of top and bottom layer. The coefficient of permeability of middle layer (2K) is twice that of top and bottom layer (K). What is the average coefficient of permeability for this flow ?

In the set up shown in the above figure, assuming the specific weight of water as 10, 000 N/m^{3}, the pressure difference between the points A and B will be

The ratio of the "standard error of a single observation of unit weight" to the standard error of the arithmetic mean of 'n' observation all of unit weight, will be

If the azimuths of the two tangents to a circular curve of radius 100 m are due north and due east, then the area bounded by the two tangents and the circular curve will be