题目

在如图的七个圆圈内各填一个数，要求每一条直线上的三个数中，当中的数是两边两个的平均数，现在已经填好两个数，那么X是多少﹖ 答案：解：根据题意，每一条直线上的三个数中，当中的数是两边两个的平均数，所以图中含有数d的所有直线的两边的数之和相等，所以a+11=13+x，因此a=x+2；所以13+b=2a=2x+4，得b=2x﹣9；因为13+11=24，所以c=24÷2=12，所以b+c=2x﹣9+12=2x+3；又因为b+c=13+x，所以2x+3=13+x，得x=10．答：那么x是10． Illegal removal of coral(珊瑚) along Sri Lanka’s coastline increased the amount of destruction on the island by last December’s tsunami, say researchers. Harindra Fernando, a fluid dynamicist (力学家) at Arizona State University in Tempe, made the connection after a visit to his native Sri Lanka earlier this year. While serving as a scientific expert and translator for a BBC-documentary team, he chatted with locals who said they saw the tsunami turn sideways when it hit coral—which would have made it less powerful than in coral-free areas. Fernando linked this to trucks he had seen last year carrying piles of coral away from the sea. Using the eyewitness reports, estimates (估算) of wave heights, and a series of divers to check the presence or absence of corals, Fernando and his colleagues produced a map of coral gaps and wave flooding along Sri Lanka’s southwest coast. The tsunami reached significantly farther inland through the gaps: in one instance, the water traveled 1.5 kilometres long and knocked a passenger train off its tracks, killing 1,700. But only a few kilometers away, where the coral was still undamaged, the wave travelled just 50 metres inland and caused no deaths. There is a similar phenomenon. In Nicaragua in 1992, a tsunami poured through a break in the coral reef made to let boats through. “Within this passage, water went one kilometre inland,” says Fernando. “But nearby, where the coral was undamaged, there were still beach umbrellas standing.” In Sri Lanka, coral is illegally mined to provide souvenirs for tourists, or to be used in house paint. Coral harvesters sometimes blow it up with dynamite (炸药) in order to collect fish at the same time. Often, the reefs in the best shape are those in front of hotels, as the hotel owners maintain them for the tourists. Fernando hopes that his findings will encourage the Sri Lankan government to enforce(实施) its laws against coral mining. 1.Harindra Fernando did all the following EXCEPT ________. A. serving as a translator for a BBC-documentary team B. helping the Sri Lankan government enforce its laws against coral mining C. producing a map of coral gaps along Sri Lanka’s southwest coast D. linking the coral removal with the destruction of Tsunami 2.The main idea of Paragraph 5 is that________. A. undamaged coral can greatly decrease tsunami damage B. coral-free area is a danger to passenger trains C. in general, water travels 30 times farther inland in a coral-free area D. it is urgent to enforce laws against coral mining 3.Which of the following may NOT be the cause of coral gaps? A. Boat passages.                    B. Tourists’ sightseeing.    C. Fish collecting.                  D. Tourists’ souvenirs. 4.Which of the following would be the best title for the passage? A. Harindra Fernando, a Great Environment Protector B. Stop Using Coral as Souvenirs C. Coral Cried “Help! Help!” D. Coral Mining Enhanced (加剧) Tsunami Damage