Question: You work at a factory that produces dumbbell weights for lifting. One of the 10 machines has been producing weights that are always 1 pound less than the rest of the machines. You have a large scale used to weigh the weights for quality control. How could you find the defective machine by using the scale only once? You are allowed to make as many weights with the machines as you please.
Answer: From each machine you make a different number of weights and however many pounds the scale is off from what it should be corresponds to the machine that made that many weights.
From machine 1 you make 1 weight, machine 2 you make 2 weights...
If the machine is off by 1 pound you know it was machine 1 that was off.
Question: A man is found dead on a Sunday morning. His wife calls the police immediately. The police question the wife and staff. The wife said she was asleep, the cook said he was cooking breakfast, the gardener said she was picking vegetables, the butler said he was cleaning the closet, and the maid said she was getting the post. The police immediately arrested the murderer.Who was the murderer?
Answer: The maid because there's no post on Sundays.