急求09年美国数学建模C题的论文

Easy to overlook the answer"

Fact is stranger than fiction, we also have many interesting mathematical kingdom. For example, in the ninth book, I now have a problem in the workbook, education, said: "this is a passenger train to the west, the east from 45 kilometers per hour line, stop, then after 2.5 hours just what the halfway point of the two cities from 18 km, two things WangXing? How many kilometres from town with the small English in this problem, the calculation method and the results are not the same. XingSuan king of the number of kilometers than small calculates km less, but the results of the two to say. This is why? You want to come? You count them two listed in the results." Actually, this problem is we can very quickly made a kind of method is: 45 x 2.5 = 112.5 (km), 112.5 + 18 = 130.5 (km), 130.5 * 2 = 261 (km), but look close scrutiny, he felt something was wrong. Actually, here we overlooked a very important conditions, "this is just w