Question: Is there a limit to the number of tiles a city can work? I've noticed that I can purchase and use tiles several spaces away from my city. How far can I go?

Answer: 
Up to 3 hexes away, 36 hexes total
----------------------------------

Plus one more for the hex the city is on.

***Civilization 5***

![alt text](https://i.stack.imgur.com/MLH64.jpg)

All of the previous games in the Civilization Series used squares for the grid, and the maximum city radius was *2ish* squares away. Take a look at the image below for what I mean by *2ish*. (In words, the exact city radius is a 3x3 grid centered on the city, with one square from each corner removed.) That was a total of 20 squares, plus one more for the city square.

***Civilization 4, and earlier***

![alt text](https://i.stack.imgur.com/5LGg3.jpg)
The maximum limit is five tiles, but thats for very large, isolated(more resorces) cities and usually your capital.