题干

如图是一个三阶幻方,由9个数构成并且横行,竖行和对角线上的和都相等,试填出空格中的数.



﹣3



7

9


5

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答案(点此获取答案解析)

解:∵﹣3+7+5=﹣3+12=9,

∴三个数的和为9,

第三行中间的数是9﹣(9+5)=﹣5,

最中间的数是9﹣(﹣3+9)=3,

第二列最上边的数是9﹣(﹣5+3)=9+2=11,

第一行的第一个数是9﹣(﹣3+11)=9﹣8=1,

第一列的第二个数是9﹣(1+9)=﹣1.

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阅读理解

    The Israeli farmers who pioneered the revolutionary technology known as drip irrigation weren't trying to solve one of the world's most urgent problems.They were just trying to survive.They lived in the desert,and they didn't have enough water to grow their crops.

    In its simplest form, it was little more than a pipe with holes in it. But behind each hole was a hi-tech dripper that let out just the right amount of water. Snaked along a row of crops so that the holes were positioned directly above the roots, the pipe could direct each precious drop of water directly to the plants, getting a bigger harvest while using a very small amount of the water.

    Over time, the farmers improved upon the technology, perfecting the drippers that regulated the flow of water, and connecting the pipelines to computers that could determine exactly how much water each plant needed and when.

    If the global population kept growing, the rest of the world would increasingly resemble their little community in the desert. So they began selling their irrigation systems in other parts of the world,eventually expanding to more than 110 countries. Netafirm, the company says it's lifting people out of poverty and conserving water at a time when the importance of doing so has never been clearer.

    The mass adoption of drip irrigation won't save the world by itself. To avoid the coming catastrophe, nearly everybody will, in some way, have to do more with less, perhaps through accepting and using other new technologies. Otherwise, it's going to get ugly.