a rectangular swimming pool 20m wide ,60 m long and 4m deep ,contains 800m3 of water.How much more water has to be added so that the water level is 30cm from the top?

First, we need to calculate the total volume of the swimming pool. The volume of a rectangular prism (which is the shape of the pool) is calculated by multiplying the length, width, and height.

The pool is 20m wide, 60m long, and 4m deep. So, the total volume of the pool is 20m * 60m * 4m = 4800m^3.

The pool currently contains 800m^3 of water.

The question asks how much more water is needed to fill the pool until it is 30cm from the top. 30cm is 0.3m. So, the volume of the pool that needs to be filled is the total volume minus the volume of the 30cm space at the top.

The volume of the space at the top is 20m * 60m * 0.3m = 360m^3.

So, the volume of the pool that needs to be filled is 4800m^3 - 360m^3 = 4440m^3.

The pool already contains 800m^3 of water, so the amount of water that needs to be added is 4440m^3 - 800m^3 = 3640m^3.

So, 3640m^3 of water needs to be added to the pool to fill it until it is 30cm from the top.