Many people are under the assumption that infinity divided by infinity is equal to 1. It extremely important to note that this is not the case.
Infinity times any number is undefined. Thus we come to the conclusion that infinity divided by any number is also undefined.
To put it into perspective, think of it this way: since it is an infinite number, you can never reach the answer because there well always be a greater number.
To sum up: infinity divided by infinity is undefined.
Hope this helped! :)