whats his account number?

Question

A curious mathematician noticed that his nine-digit Swiss bank account number used all of the digits 1 through 9 exactly once. Furthermore, the first two digits formed a number divisible by two, the first three digits were a number divisible by three, and so on. Unfortunately, a few years later when needed to access his account – which is available only to someone who knows the number – he couldn’t remember the number nor find the paper on which he had written the number. All he could remember were the relationships described above. Can you help him find his account number?

Answer 1

Start by drawing 9 lines, one to represent each number in the code.  Then think about the divisibility rule.  Ex: a number divisible by 2 will end in an even number, for a number divisible by 3, you add all the digits together, and if it is a multiple of 3, then the whole number is a multiple of 3.  

 

You should be able to place the 5 right away.  Then go through an right now the possible numbers for each spot under the line.  Cross them out as you place numbers.  You may have to guess to start, but mark where you guess, so you know where to go back to.  Keep working through the places until all the numbers work!

Answer 2

I suggest he use the number

381654729

You can check if it follows all conditions.