Homework Seven Quick Answers
1. 2*(26
3*10
3) [5.1.18]
2. You can choose 21*21 integer pairs. In the given range 11 are even, 10 are odd. So: (11*11 + 10*10)/21*21 [5.1.20]
3. Count the numbers from 00000 to 99999 - how many 5's appear? C(n,1)*9
4+C(n,2)*9
3+C(n,3)*9
2+ C(n,4)*9
1 + 1. [5.1.30]
4.(n+1)
4 - 1 -- you can pick 0 .. n of any letter, but you can't pick all 0s (hence the - 1 term)
5. 7! / 2!
6. C(26,6)
7. (13!)
4 / ((52!)/(4!)
13)
8. 20*19*18...*11
9. 4! * (5*6*7)
10.
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RobbieMoll - 2012-04-26