Problem:
What is the largest factor of that does not contain the digit or ?
Problem:
What is the largest factor of that does not contain the digit or ?
Solution:
If the number is a multiple of , then its units digit will be either or . Hence, the largest such number must have no factors of .
We have . Removing every factor of , we get that our number must be a factor of .
If our number contains a factor of , we cancel the factor of from , , and until we get . Otherwise, the largest number we can have is . We conclude that the answer is .