Felecity cannot remember the correct order of the five digits in her ID number. She does remember that the ID number contains the digits 5, 0, 3, 7, 4. What is the probability that the first three digits of Felecity’s ID number will all be odd numbers?

Question

anonymous · Answer

OK, take the total number of possibilities and then find how many fit the conditions, then divide the two for the probability. This is an ordering of five problem, meaning there are 5 ways to choose the first, 4 for the second, 3 for the third, 2 for the fourth, and the last is just whatever's left. Multiply those for the total number of possibilities. There are 3 odd numbers here, so some combination of them would have to be the first three. Three choices for the first, two for the second, one for the third, multiply that and divide by the previous product.

primeralph · Answer

..............wish it was her ATM pin.