Solving Problems Submitted to MAA Journals (Part 4) – Mean Green Math
The following problem appeared in Volume 96, Issue 3 (2023) of Mathematics Magazine. Let $latex A_1, \dots, A_n$ be arbitrary events in a probability field. Denote by $latex B_k$ the event that at least $latex k$ of $latex A_1, \dots A_n$ occur. Prove that $latex \displaystyle \sum_{k=1}^n P(B_k) = \sum_{k=1}^n P(A_k)$. I'll admit when I…