This is my first post.
The question I'm working on is, 'All the digits of a number are different, the first digit is not zero, and the sum of the digits is 36. There are N x 7! such numbers. What is the value of N?'
I think I have figured out that 1,9,2,8,3,7,6 gives me 7! Then there is 3,7,4,6,2,8,1,5, which gives me 8!. I can add and factor to get 9 x 7!. Now I need to include the zero. That gives me both 8 and 9 digit numbers but the zero can't be in the first place. I haven't studied permutations and am not sure how to proceed. I think I would do 8! and 9! respectively and subtract something but I can't get my head around that difference.
If someone could point me in the right direction it would be very much apprecaited.