A discrete mathematics problem by Durgesh Tiwari
Kamlesh writes a letter to his friend from Delhi. It is known that one out of 10 letters that are posted does not reach its destination. If Kamlesh does not receive the reply to his letter, then what is the probability that Navneet did not receive Kamlesh's letter? It is certain that Navneet will definitely reply to Kamlesh's letter if he receives it.