In the US there usually 20 in a pack, 200 in a carton.
20
There are 10 packs of cigarettes in a carton. There are 200 cigarettes in a carton and 20 in a pack making it 10 packs a carton.
In the pack, there are (per tobacco industry report) 599 chemicals. When the cigarette burns, however, chemical reactions occur and many other chemicals are created--hence the 4000 chemicals in...
Your average pack of cigarettes has twenty too many cigarettes.