I need someone to solve me a problem, but I need step by step results with detailed explanations. Use calculus or whatever you need to solve it.
You have a tank of 40gallons of clean water, you add 1 gallon of dirty water and then take one gallon out of the tank. You always remain with 40 Gallons.
You repeat this several times, (put 1 galon of dirty and then take one gallon out).
The questions is, How many time do you have to repeat this process in order to have 50% or more dirty water in the tank???