50 Challenging Problems in Probability [Part 14]: Collecting Coupons

The probability of getting a distinct number from the next box is now 4/5. No. of additional box to get the second number = 1/(4/5) = 5/4. (One can show that the expected value for the number of independent trials to get the first success is 1/p.) The probability of getting a distinct number from the next box is now 3/5. No. of additional box to get the third number = 1/(3/5) = 5/3. The probability of getting a distinct number from the next box is now 2/5. No. of additional box to get the third number = 1/(2/5) = 5/2. The probability of getting a distinct number from the next box is now 1/5. No. of additional box to get the third number = 1/(1/5) = 5. <a href="https://medium.com/@shelvia1039/50-challenging-problems-in-probability-part-14-collecting-coupons-d946ec192c55">Website</a>