#### 题目列表

A 3-digit integer is formed by 3 different integers selected from 1,2,3,4,5. How many different such 3-digit integer?

There are 200 people, shown as the following graph. Now choose one person from each of sophomore,junior,senior to form a committee, how many combinations will there be?
n is the number of a 3-digit integer which has at least two "1"in its digits.

n

#### Quantity B

29

Among the 300 students who sign up for a course, 9% are sophomore, 3% are junior and 1% is senior. If a teacher randomly selects 3 students form them, then how many different combinations of a sophomore student, a junior student and a senior student will be there?
In how many different ways can we use 0, 1, 2, 3, 4, to form a 4-digit number which must be a multiple of 3 (None of the five numbers can be used more than once)?
S={1, 2, 3, 4, 6}

T={1, 2, 3, 6, 8}

x is a number in set S, and y is a number in set T. What's the total number of all the different possible values of the product of x and y?
Use five numbers 3, 4, 6, 7, 9 to form a five-digit number (each number can only be used once). How many different five-digit numbers are possible if the hundred-digit number must be an odd number?
The hundreds digit and tens digit of a three-digit integer $n$ is odd and even,respectively. If the units digit is a number different from other two digits, what is the number of the possible value of $n$?
A 4-digit integer is formed by four integers selected from 0, 1, 2, 3 and the same figure can be repeatedly used. If the sum of the 4 digits is 3, how many different integers can be formed?
A 4-digit integer is formed by four integers selected from 0, 1, 2, 3, 4 and the same figure can be repeatedly used. If the sum of the 4 digits is 4, how many different integers can be formed?
Which of the following is a perfect square?
n is a positive even integer.

#### Quantity A

$\frac{n!}{(n-2)!}$

#### Quantity B

$(2)(\frac{n}{2})!$

A password is formed by 5 different letters (A, B, C, D, E), if no letter can be repeated in one password, how many different passwords can be formed?
How many 5-digit odd integers can be formed out of 3, 4, 6, 7, 9 such that each number is used for only once?
A father purchased theater tickets for 6 adjacent seats in the same row of seats for himself, his wife, and their 4 children. How many seating arrangements are possible if the father and mother sit in the 2 middle seats?
A students selects books for reading material randomly,and which of the following has exactly 10 different ways of selection?
Indicate all such statements.
S={1, 3, 5, 7,.............,397, 399}

Set S consists of the odd numbers from 1 to 399, inclusive. How many different ordered pairs (p, t) can be formed, where p and t are numbers in S and p < t? (Note: The sum of the integers from 1 to n, inclusive, is given by the formula $\frac{n(n+1)}{2}$ for all positive integers n.)
There are four people, S, M, K and R. Some people should be selected from these four people to form a committee. The committee is required to have at least two people. How many different methods are there in total?
Two boys and two girls are selected from six boys and four girls. How many methods are there?
There are four books A, B, C, and D, how many arrangements if A and B must be next to each other?

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