题干

四张扑克牌(方块2、黑桃4、黑桃5、梅花5)的牌面如图l,将扑克牌洗匀后,如图2背面朝上放置在桌面上.小亮和小明设计的游戏规则是两人同时抽取一张扑克牌,两张牌面数字之和为奇数时,小亮获胜;否则小明获胜.请问这个游戏规则公平吗?并说明理由.

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答案(点此获取答案解析)

解:此游戏规则不公平.

理由如下:

画树状图得:

共有12种等可能的结果,其中两张牌面数字之和为奇数的有8种情况,

所以P(小亮获胜)=

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阅读理解

    Researchers at Stanford University have developed a new material that can move heat out of buildings and into space. The researchers say the material can cool buildings even on hot days. The cooling material is a very thin sheet with many layers that could be placed on a roof like solar panels(板). However, instead of turning sunlight into energy as solar panels do, the material turns heat into infrared(红外线的)radiation.

    Shanhui Fan is an electrical engineering professor at Stanford University. He says that the panels have a layer of material that is like sand. The panels act like a mirror. They take heat out of buildings and reflect the light from the sun. And he says both the heat and sunlight arc sent 100 kilometers into outer space. "It's a structure that cools itself without electricity input, even under the sun. So, what it does is basically radiate heat to outer space and also reflect the sunlight so it doesn't get heated up by the sun. Mr. Fan says it is like having a window into space. The heat is sent directly into space without increasing the air temperature

    He says buildings in developing countries that do not have electricity or air conditioning could use the panels. "In areas where electricity is out of reach for many people, there is a potential benefit for storing medicine or even food. In many of these situations, being able to reduce the temperature is important. And this would provide a way to do it.”

    The researchers say the main problem is creating actual cooling systems using the high-tech panels. They say it may be possible to develop a cooling spray(喷涂)that could be used on present solid structures. They believe the cooling spray technology could be developed in the next three to five years. They say as much as 15 percent of the energy used in the United States is spent providing power to air conditioning systems.