I have found this statement ,can you help me to prove this.
If an integer is not divisible by 2 or 5, some multiple of that number in decimal notation is a sequence of only a digit.
OBJECTIVE: Now you are given the number and the only allowable digit, you should report the number of digits of such multiple.
For example you have to find a multiple of 3 which contains only 1's. Then the result is 3 because is 111 (3-digit) divisible by 3. Similarly if you are finding some multiple of 7 which contains only 3's then, the result is 6, because 333333 is divisible by 7.