題目問題

NO.PZ2021062201000008问题如下 GerSturm wants to sponsor a contest with a $1 million prize. The winner must pithe stocks thwill the top five performers next yeamong the 30 stocks in a well-known large-cstoinx. He asks you to estimate the chances thcontestants cwin the contest. Whare the chances of winning if the contestants must pithe five stocks in the correorr of their totreturn? If choosing five stocks ranmly, a contestant’s chanof winning is one out of: A.142,506B.17,100,720C.24,300,000 B is correct. The number of permutations is the number of ways to pifive tocks out of 30 in the correorrnPr=n!(n−r)!{}_n{P_r} = \frac{{n!}}{{(n - r)!}}n​Pr​=(n−r)!n!​30P5=30!(30−5)!=30!25!=30×29×28×27×26=17,100,720{}_{30}{P_5} = \frac{{30!}}{{(30 - 5)!}} = \frac{{30!}}{{25!}} = 30 \times 29 \times 28 \times 27 \times 26 = 17,100,72030​P5​=(30−5)!30!​=25!30!​=30×29×28×27×26=17,100,720 老师，第一大段看不明白，可以翻译吗？

NO.PZ2021062201000008问题如下 GerSturm wants to sponsor a contest with a $1 million prize. The winner must pithe stocks thwill the top five performers next yeamong the 30 stocks in a well-known large-cstoinx. He asks you to estimate the chances thcontestants cwin the contest. Whare the chances of winning if the contestants must pithe five stocks in the correorr of their totreturn? If choosing five stocks ranmly, a contestant’s chanof winning is one out of: A.142,506B.17,100,720C.24,300,000 B is correct. The number of permutations is the number of ways to pifive tocks out of 30 in the correorrnPr=n!(n−r)!{}_n{P_r} = \frac{{n!}}{{(n - r)!}}n​Pr​=(n−r)!n!​30P5=30!(30−5)!=30!25!=30×29×28×27×26=17,100,720{}_{30}{P_5} = \frac{{30!}}{{(30 - 5)!}} = \frac{{30!}}{{25!}} = 30 \times 29 \times 28 \times 27 \times 26 = 17,100,72030​P5​=(30−5)!30!​=25!30!​=30×29×28×27×26=17,100,720 老师好，请问为什么要剪5之后排列？

NO.PZ2021062201000008 17,100,720 24,300,000 B is correct. The number of permutations is the number of ways to pifive tocks out of 30 in the correorr nPr=n!(n−r)!r!{}_n{P_r} = \frac{{n!}}{{(n - r)!r!}}n​Pr​=(n−r)!r!n!​ 30P5=30!(30−5)!=30!25!=30×29×28×27×26=17,100,720{}_{30}{P_5} = \frac{{30!}}{{(30 - 5)!}} = \frac{{30!}}{{25!}} = 30 \times 29 \times 28 \times 27 \times 26 = 17,100,72030​P5​=(30−5)!30!​=25!30!​=30×29×28×27×26=17,100,720 从题里面，哪里可以看出是需要排序的呢？

NO.PZ2021062201000008 17,100,720 24,300,000 B is correct. The number of permutations is the number of ways to pifive tocks out of 30 in the correorr nPr=n!(n−r)!r!{}_n{P_r} = \frac{{n!}}{{(n - r)!r!}}n​Pr​=(n−r)!r!n!​ 30P5=30!(30−5)!=30!25!=30×29×28×27×26=17,100,720{}_{30}{P_5} = \frac{{30!}}{{(30 - 5)!}} = \frac{{30!}}{{25!}} = 30 \times 29 \times 28 \times 27 \times 26 = 17,100,72030​P5​=(30−5)!30!​=25!30!​=30×29×28×27×26=17,100,720 ​您好，按照我的理解，这道题的题干第二段包含两个问题，第一个问题是排列问题，选择B，第二个问题是组合问题，随机从30支股票中选出5个，答案选择A？