问题 填空题

某国家代表队要从6名短跑运动员中选4人参加亚运会4×100m接力,如果其中甲不能跑第一棒,乙不能跑第四棒,共有______种参赛方法.

答案

由题意知本题是一个排列组合及简单计数问题,

从六人中取四人参加的种数为A64

去掉甲、乙两人中至少有一人不排在恰当位置的有C21A53种,

因前后把甲、乙两人都不在恰当位置的种数A42减去了两次.

故共有A64-C21A53+A42=252种

故答案为:252

单项选择题
单项选择题

It was the best of times or, depending on your political and philosophical outlook, one of the foulest and most depraved. Rebellion seemed to be leaping from city to city, continent to continent, by some fiery process of contagion. Radical students filled the streets of Mexico city, Berlin, Tokyo, Prague. In the U. S. , Chicago swirled into near anarchy as cops battled antiwar demonstrators gathered at the Democratic Convention. And everywhere from Amsterdam to Haight-Ashbury, a generation was getting high, acting up.

So, clearly, it was the year from hell--a collective "dive into extensive social and personal dysfunction," as the Wall Street Journal editorialized recently. Or, depending again on your outlook, a global breakthrough for the human spirit. On this, the 25th anniversary of 1968, probably the only thing we can all agree on is that ’68 marks the beginning of the "culture wars," which have divided America ever since.

Both the sides of the "culture wars" of the ’80s and ’90s took form in the critical year of’68. The key issues are different now--abortion and gay rights, for example, as opposed to Vietnam and racism--but the underlying themes still echo the clashes of ’68: Diversity vs. conformity, tradition vs. iconoclasm, self-expression vs. deference to norms. "Question authority," in other words, vs. "Father knows best."

The 25th anniversary of ’68 is a good time to reflect, calmly and philosophically, on these deep, underlying choices. On one hand we know that anti-authoritarianism for its own sake easily degenerates into a rude and unfocused defiance: Revolution, as Abbie Hoffman put it, "for the hell of it." Certainly ’68 had its wretched excesses as well as its moments of glory: the personal tragedy of lives undone by drugs and sex, the heavy cost of riots and destruction. One might easily conclude that the ancient rules and hierarchies are there for a reason--they’re worked, more or less, for untold millenniums, so there’s no point in changing them now.

But it’s also true that what "worked" for thousands of years may not be the best way of doing things. Democracy, after all, was onee a far-out, subversive notion, condemned by kings and priests. In our own country, it took all kinds of hell-raising, including a war, to get across the simple notion that no person is morally entitled to own another. One generation’s hallowed tradition--slavery, or the divine right of kings--may be another generation’s object lesson in human folly.

’68 was one more awkward, stumbling, half-step forward in what Dutschke called the "long march" toward human freedom. Actually, it helped inspire the worldwide feminist movement.

To which of the following is the writer most likely to agree()

A. A war brings with it nothing but destruction

B. It is wise to see the ’68 War into perspective

C. Revolution leaves a new generation acting up

D.Ancient rules are by all means reasonable