You are a junior detective investigating a case. Boys at an apartment complain that every day, they have an egg spinning competition with only raw eggs, and every day one particular boy wins.
The boys want you to find out how. You are observing the boy spinning an egg when suddenly it drops to the floor. The apartment clerk casually hands him a broom to clean it up, as if it happens every day. You now know why the boy always wins the daily competition. How?
Answer
The clerk handed the boy a broom, so the egg the boy was spinning must have been hard-boiled. If the egg was raw, the clerk would have handed the boy a mop.