25、为了美化博望中学校园环境，建设绿色校园，我校准备对校园中30亩空地进行绿化．绿化采用种植草皮与种植树木两种方式，要求种植草皮与种植树木的面积都不少于10亩，并且种植草皮面积不少于种植树木面积的三分之二．已知种植草皮与种植树木每亩的费用分别为8000元与12000元．（8分）
（2）种植草皮的面积为多少时绿化总费用最低，最低费用为多少？（4分）
（1） 种植草皮的最小面积为12亩
（2）最低费用为20×8000+10×12000=280000元
（1）关系式为：种植草皮的面积≥10；种植树木的面积≥10；种植草皮面积≥种植树木面积×
，据此列不等式组求解即可；
（2）总费用=种植草皮总费用+种植树木总费用，结合（1）中自变量的取值求解．
IV. 阅读理解：（共20题，每小题2分，共40分） A long time ago, before there was any money (coins or paper money), people got the things that they needed by trading or exchanging. Salt was one of the first items used to exchange for other items. Later, some of the common things that were used for exchanging were tea leaves, shells, feathers, animal teeth, tobacco, and blankets. Around 3000 BC, barley, a type of grain, was used for exchanging. The world’s first metal money was developed by the Sumerians who melted silver into small bars all weighing the same. This was around 1000 BC. About three hundred years later, people started using coins as official money. Around 640 BC, people in the ancient kingdom of Lydia ( which was in Turkey) created special coins of exact with and purity (纯度). They were made of gold and silver and were stamped with a lion’s head. Later, other empires such as Greece, Persia, and Rome adopted the concept of coins and started developing their own in many different shapes and different metals. Around the year 1000, the Chinese started using paper money. The Chinese were the first to use paper money. The Europeans discovered this thanks to Marco Polo who went to China in 1295. the Chinese had different values for the paper notes which were made by the Chinese government. Around 1661, Sweden became the first European country to make paper money. Until 1850, the Spanish dollar was the coin most widely used throughout the world. 1What is the best title for this passage?
A. Spain B. China C. Sweden D. Lydia |