A four-digit serial number is to be created from the digits 0 through 9. How many of these serial numbers can be created if 0 can not be the first digit, no digit may be repeated, and the last digit must be 5?

1 Answer
Aug 17, 2016

#48 # serial numbers

Explanation:

Consider the number of options for each position.

First digit: not 0, not 5. there are 8 options.#" "8xx#

Second digit: not 5. not the first digit. 8 options#" "8xx#

Third digit: not 5,not 1st or 2nd: 7 options.#" "7xx#

Fourth digit: 5. 1 option #" "1xx#

Number of unique numbers = #8xx8xx7 = 448#