Find how much the water level of the well is decreasing

[J.Eriksson]

I have a problem and I do not how to solve the problem. So please write how I should solve the question.

A water well has a diameter of 110mm. Water can be pumped from the well into the tank. Every time the pump is started 40 l of water is pumped away. Find how much the water level of the well is decreasing, ingoring the inflow of water

 

[Mark44]

What formulas do you think might be relevant to this problem? What have you tried?

These are the sections that you deleted when you posted your problem. They are there for a reason, to help you get started at solving this problem.

 

[J.Eriksson]

Well,
I solve my own problem! I did this way:
110mm is the same as 1,1dm
1,1/2=0,55 (radius)
then I use the formel πr^2
π0,55^2=0.95
40/0.95= 42dm
42dm=4,2m
Power of ten: 4,2X10^1 m