"Twenty-two," Kowalski replied.
After he left, he double-checked it on his calculator (he knew he should have taken it to the interview!) and realized he wouldn't get the job.
About two weeks later, he got a letter that said he was hired for the job! He was not one to look a gift horse in the mouth, but was still very curious.
The next day, Kowalski went in and asked why he got the job, even though he got such a simple question wrong. The boss shrugged and said, "Well, you were the closest."