[calfever]

1.a three out of five series is a competition between two teams consisting of at most five games and ending as soon as one of the two competiing teams wins three games. How many sequence of winners and losers in one series is not the same as in the other series. Draw a tree represent the possibilities.

2.How many sequences of length n can be formed using the alphabet {0,1}?
Using the alphabet {0,1,2} Using the alphabet {1,2,...,k} for k \in N?
How many possible words are there in the English language of length 13 at most?
If dictionary contains 500000words of length less than or equal to 13,what percentage of all words of length less than or equal to 13 does it contain?


ข้อ2 ลองทำดูแล้วได้แบบนี้อ่ะค่ะ
How many sequences of length n can be formed using the alphabet {0,1}?
ตอบ 2^n
Using the alphabet {0,1,2} Using the alphabet {1,2,...,k} for k \in N?
ตอบ 3^n กับ k^n
How many possible words are there in the English language of length 13 at most?
ตอบ เป็นไปได้
If dictionary contains 500000words of length less than or equal to 13,what percentage of all words of length less than or equal to 13 does it contain?
ตอบ 7.69% ?? ใช้หลักการPigeon-Holeรึเปล่าคะ --"

ช่วยอธิบายให้หน่อยค่ะ TT