Dr. Jenson writes a number on the whiteboard.
He then writes 221 to the right hand side of this number,
which ends in a new number which is a multiple of the old number.
What is the original number? -- Find all possible solutions.
Let be the original number.
If 221 is appended to the right end, the new number is: .
If this is a multiple of , we have: . . for some integer
Then we have: .
Since is an integer, must be a factor of 221.
The only factors of 221 are: .