救我的排列组合= =太烂了 Test 5 10. Set X has x members and set Y has y members. Set Z i s composed of all members that are in either set X or set Y with the exception of the k common members (k>0).Which of the follow ing represents the numbers in set Z? *看不懂k代表什麽? Ans: x+y-2k Test 7 1.Each person at a party shook hands exactly once with each other at the party. There was a total of 21 handshacks exchanged at the party. Column A: the number of people at the part. Column B: 8 *我算7 选A 可是答案是B.. 20.Four boys and three girls are arranged seatts in two rows, the first containing four seats and the second three seats. How many possible arrangements are there if the boys and the girls sit next to each other? Ans: 288 21. 同题20. How many arrangements are there if three girls sit together? Ans:840 Test 8 6.x+y+z<0 z>x+y+1 Column A: z Column B:1 Ans:D *有判断的好方法吗 8. On the real number line, the coordinate of points A, B, and C are 2, -1 and x, respectively. What is value of x when line AC^2 + line BC^2 has the least value? Ans: 1/2 21. If 5 cards, represented by A, B, C, D, and E, are placed in a row so that C is never at either end, how many different arrangements are possible? Ans:72 我算96耶@@ 全部有5!种=120 C在最後面有4!种=24 120-24=96 那边错了?? 22. How many possible committees can be formed from a group of seven people if each committee can have any numbers from one to seven? Ans: 127 Test 9 10. Which of the following is the second power of (1+1^0.5)^0.5 Ans: 2^0.5 *second power是什麽? 24. A bag contatins red gloves, black gloves and white ones. What is the least number of gloves that must be taken out of the bag to be sure of having 4 pairs of gloves? Ans:10 *不懂 --

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