题目

On New Year's Day, many people eat special foods for good 【1】. In Spain（西班牙）and some Latin American countries, people 【2】 twelve grapes（葡萄） at 12 o'clock on New Year's Eve. One grape is for good luck in 【3】 month of the new year. In the north of China, people eat 【4】. Some have coins（硬币）in them. Everybody wants to【5】the coin for luck and money in the new 【6】. Of course they don't eat the coin. Japanese eat noodles on New Year's Eve and their birthdays. 【7】they think it may bring them good luck 【8】long life.已知梯形的上底长为3cm，中位线长为6cm，则下底长为    cm．