All the best wishes to the Ukrainian people. Praying for Peace.

I´m interested in Math on school level and a little bit further. I like not only to post an answer, but to give a reply for further questions in the comments as well.

Best regards, callculus ( Nov 14 '20)

In the future I will collect some useful posts here:

• inclusion–exclusion principle /formula interpretation
• Incorrect law of total probability
• Solving equation that contains cdf and pdf of standard normal distribution
• No. of fishermen who caught at least n fish
• Linear regression for exponential function
• ODE: Variation of parameters in general
• Entropy-measure-and-herfindahl-index
• Painter, plumber and electrician build an economy
• Completing the square to get a normal distribution term
• Sensitivity analysis / Linear programming
• Unbiased estimator for the variance-proof
• Summand of the binomial theorem
• Fraction of normally distributed r.v.'s is Cauchy distributed
• Joint-distribution of uniformly iid random variables
• St. Petersburg paradox
• Joint pmf of binary random variables
• Formula for approximation the cdf of the normal distribution
• Function with constant elasticity
• Same birthday of two people
• Wrong Law of total probability
• Calculation of negative growth rates
• Average growth rate in n steps and different rates
• Generating function