[計量] 還是數學問題...
排列組合的問題
一樣是在gre guide上的practice question
1. A teacher prepares a test. She gives 5 objective type questions out of
which 4 have to be answered. Find the total ways in which they can be
answered if the first 2 questions have 3 choices and the last 3 have 4
choices.
A: 816
2. How many 5 digit numbers are there with distinct digits?
A: 27216
3. How many five digit numbers can be formed using the digits 0,2,3,4 and 5,
when the repetition is allowed such that the number formed is divisible by
2 or 5 or both?
A: 1500
4. In a school 5 colors are allotted to each house. If the flag of Tagore
House has to be a sequence of three blocks of different colors, then how
many colors can they choose from?
A: 60
我都有嘗試去解，但是就算湊巧算出正確答案也不知道為什麼.... orz
謝謝...
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