Hand-rolled cigarettes were once very popular, as buying tobacco and paper, and rolling your own was much cheaper. This puzzle dates back to those times.
An even cheaper way of smoking was to collect the ends of hand-rolled cigarettes (known as dog ends) and extract the tobacco from them. This removed the need to purchase your own tobacco.
One person knew that he needed seven dog ends to get enough tobacco to roll one cigarette. One day he collected 49 dog ends - how many cigarettes did he roll and smoke from these?
At first glance it would seem that 49 dog ends would produce seven hand rolled cigarettes. This is indeed correct, but those seven cigarettes would produce seven dog ends, which would be sufficient to produce one more.
He rolled and smoked eight cigarettes.