it is a long sorty about 二百五. In the acient Zhan dynasty, Qin was the strongest country, and always invaded other countries. One famous politician called Su Qin persuaded other countries unite to fight Qin,but he was killed by a murder from QIn. The king of Qi(belong to the union) was so angery, he thought out a methord to find the murder. So he announced: Su Qin is a spy, I also want him die, now somebody killed him, and removed the evil, so I want to give the person one thousand liang (A unit of weight)gold as rewards. Then four people wanted the money , they didn't know it was a strategy of the king, and they cheated to the king , said Su Qin was killed by them The king was angery but he still asked:there are one thousand liang (A unit of weight)gold, how can I give to four people . One cheater said: divided by four, 250 per people.at last the four person were killed by the king, and the real murder still alive. so today we use 250 as idiot.