- #1
- 19,443
- 10,021
Submitted by @PeroK
Consider all 7-digit numbers which are a permutation of the digits 1-7. How many of these are divisible by 7?
Can you prove the answer algebraically, rather than simply counting them?
Please make use of the spoiler tag
Consider all 7-digit numbers which are a permutation of the digits 1-7. How many of these are divisible by 7?
Can you prove the answer algebraically, rather than simply counting them?
Please make use of the spoiler tag