Skip to main content
OlympiadHQ

Browse · MATH

Print

jmc

counting and probability intermediate

Problem

A palindrome is a number which reads the same forward as backward. How many five-digit palindromes can be made from the digits 1, 2, and 9? (Each digit may be used more than once.)
Solution
A five-digit palindrome would be of the form , where , , and are digits (not necessarily distinct) from to (with from to ). We have three possibilities for each of , and which gives us possible palindromes.
Final answer
27