Question

A bank’s ATM card requires that a customer set a four digit pin number. Each digit may be any number from 0 to 9. How many guesses would it take to achieve a 50% probability of guessing a customer’s pin number if you knew that the customer had set it based on a date (MMDD)?

Answer 1

k

Answer 2

So, I have 4 slots to fill. The first has 2 options, and the second has 9. So, I'm assuming I start 2x9. The next two slots would be 3 and 9; no?

Answer 3

@freckles

Answer 4

@phi