MathDB

5

Part of 2015 Math Prize for Girls Problems

Problems(1)

Math Prize 2015 Problem 5

Source:

9/22/2015
How many distinct positive integers can be expressed in the form ABCDāˆ’DCBAABCD - DCBA, where ABCDABCD and DCBADCBA are 4-digit positive integers? (Here AA, BB, CC and DD are digits, possibly equal.) Clarification: AA and DD can't be zero (because otherwise ABCDABCD or DCBADCBA wouldn't be a true 4-digit integer).