This is a gem of a puzzle that my nephew, Karan, gave to me yesterday. He and I came up with different ways to come to the answers, and there are probably many more ways.
For all the possible 5 digit numbers with the digits 1, 3, 5, 7 and 9. Each of the digits can appear only once in a number and all of them need to appear in every number (therefore 11379 is not a valid numbers). What is the addition of all these numbers?
As always, please send your answers as comments within the blog (preferred), or send an e-mail to email@example.com. Please do share the puzzle with others if you like, and please also send puzzles that you have come across that you think I can share in this blog.