[問題] 離散請教
1. how many solutions are there to the equation X1+X2+X3+X4+X5=21,
where Xi, i=1,2,3,4,5 is a nonnegative integer such that 0<=Xi<=10
求整數解個數跟求非負整數解個數一樣嗎? 求整數解我會
但求非負要怎麼求阿?
2. There are _________ consecutive 0s at the end of the binary expansion
of 70!
3. there are ________4-digit decimal telephone numbers haviing one or
more repeated digits.
4. if there are five possible grades, A,B,C,D,and F, the minimum number of
students required in a class to be sure that at least six will receive the
same grade is ________________.
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