# Sunday Times Teaser 2611 – Simple Arithmetic

*by Danny Roth*

#### Published: 7 October 2012 (link)

George and Martha are teaching their great-grandchildren some simple arithmetic. “If you add two thirties to four tens you get a hundred,” George was saying, and he wrote it like this:

“Strangely,” added Martha, there are nine different letters there, and if you allow each letter to stand for a different digit, there is a unique sum which works.”

Which digit would be missing?

4 Comments
Leave one →

Here is my solution:

A different approach using permutations:

Here is a further development of Geoff’s solution that is very fast on pypy:

As part of the joint effort, I think we should give some credit to Naim. I had seen him permute individual digits from letters to make larger numbers on Jim Randall’s Enigma site. I thought it was a method worth trying for this teaser.