Question

the mud taken out from a pond is spread equally in a field .if the pit dug out in a pond is 200m long ,50m wide and 0.75m deep then how much high will be the land field.

Answer 1

You have to understand Volume and Area. The total volume of water in the pond is the product of the length, width and depth. The unit is cubic feet. The surface area is the product of the length and the width. The unit for area is square feet. 
Total volume = 200 ft x 100 ft x 20 ft = 400,000 cubic feet. 
Since 40,000 cubic feet of water evaporated, the volume of water left = 400,000 - 40,000 = 360,000. 
Recognizing that the length and width of the pond do not change during evaporation, area of the pond is 200 ft x 100 ft. = 200,000 square feet. Dividing the volume by the surface area will give you the new depth of the pond. 
New depth = 360,000/200,000 = 18 ft. 
The drop of the water level will be 20 ft - 18 ft = 2 ft. That is your answer.

Answer 2

1 divied 200 ×50×0.75÷100= 7500

To find hieght (h×h) 7500÷b1×b2

7500÷300×50= 0.5m ( 50cm)