Question

for any positive natural number n that has a prime factorization without the numbers {2,5}is it possible to multiply it by another number such that the result is a string of nines? note that the number of nines does not matter, what matters is that the result is just nines.

Answer 1

for 1 - 1*9=9
for 3: 3*3=9
for 7: 7*7=49
for 9: 9*1=9

Answer 2

for 11: 11*9=99
for 13: 13*?=????

Answer 3

The issue with this question is how to find such a given number

Answer 4

*for 7: gimme a sec.

Answer 5

for 7: 7*142857=999999

Answer 6

Btw, I think I'll make this my problem of the day. It's simple math washed up a little so you don't recognize it.

Answer 7

@apoorvk