Fulfilling The Wish Of Cigarette Smoking

What was the challenge? 

Bruce takes 9 of his 10 cigarette butts and make 3 cigarettes using those 9 (9/3=3). Now, he smokes all 3 cigarettes. At this point, he has 3 + 1 = 4 cigarette butts.

Using 3 out of 4 cigarette butts, he make one another cigarette and smokes it. Now he has 1 + 1 = 2 cigarette butts & till now has smoked 4 cigarettes.

Now he borrows 1 Tom's cigarette butts making total number of cigarette butts equal to 3. Using these 3 butts he makes one more cigarette and this way he smokes 5th cigarette. 

After smoking this 5th, he puts back the cigarette butt left in Tom's pile so that Tom won't find anything missing.