Find the smallest number comprised of only 3’s and 7’s which fits the following conditions:

1) It has at least one 3;
2) It has at least one 7;
3) It is divisible by 3;
4) It is divisible by 7;
5) The sum of its digits is divisible by 3;
6) The sum of its digits is divisible by 7.

The official answer is correct.

The explanation is not

 Rules 2 and 4 are NOT equivalent (0 is divisible by any number, including 7).

 Rules 3 and 5 are  equivalent .

Posted by Ady TZIDON on 2014-11-20 22:40:59