nCr and nPr(5m)

2010-08-08 8:31 pm
I need steps. thank you. 5 marks

1. There are 32 teams entering a soccer competition. They are divided into 8 groups (A-H) with 4 teams in each group for group stage. The top two teams in each group will enter he round of 16, and a list can be formed. How many different lists can be formed?

Solutions: 429 981 696


2. It is known that the password for an ATM card must be formed by 6 numbers from 0 to 9, and the numbers used can be repeated. Mr. Wong is going to choose 6 different numbers to form the password. A hacker tries to find out the password of Mr. Wong by trails and errors. It is given that the time required for testing one trail is 10^(-2) seconds. How long does the hacker take to find out the password of Mr. Wong in the worst case?

Solutions: 10,000 seconds.

3. Didi's mother has 6 different cartons of juice and 4 different cans of soft drinks. She puts 4 cartons of juice and 2 cans of soft drinks into the refrigerator in a row. Find number of arrangements.
Solutions: 64 800


4. In a lucky draw, 22 participants are male and 18 are female.
How many arrangements are there for 3 participants wining the first prize, second prize and third prize, given that exactly 2 winners out of 3 are male?

Solution: 24 948

回答 (1)

2010-08-09 9:58 pm
✔ 最佳答案
1) 4P2 cases for each group , there are 8 groups ,(4P2)^8= 429 981 696 different lists can be formed.
2)The hacker does not know Mr. Wong is going to choose 6 different numbers to form the password.The hacker try all cases including repeated number password.= 10^6 casesNeed (10^6)(10^-2) = 10^4 = 10 000 seconds.
3)(6C4)(4C2) (6P6) = 64 800
4)(22C2)(18C1) (3P3) = 24 948


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