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How many points (r, s) can be formed so that r < s, and that the x and y-coordinates of the point are both selected from odd integers between 1 and 399, inclusive?
Two boys and two girls are selected from six boys and four girls. How many methods are there?
In how many different ways can 5 identical small balls be placed in 3 different baskets so that each basket must have at least one small ball?
There are four books A, B, C, and D, how many arrangements if A and B must be next to each other?
A, B, C, D and E need to take seats such that A and B sit next to each other. How many ways can they arrange the seats?
Four different books A, B, C, D are to be placed on the shelf, A and B must be put together. How many different ways can the four books be placed?
Four different toys need to be put into three different kids. At least one toy should be given to each kid. In how many ways can these toys be arranged?
If there are 6,840 different ways when promoting 3 out of 20 employees for three different positions, then in how many ways can 3 employees be selected out of 20 for three identical positions?
How many different 5-digit numbers can be formed by one "1",two "2",and two "5"?
The 8 items A, B, C, D, E, F, G, and H are to be displayed on a straight line. In how many ways can the items be displayed if item B must be placed in any position that is to the right of item A,and item C must be placed in any position that is to the right of B?
Someone rearranges all the letters from the word "Mississippi"

Quantity A

The probability that all the same vowel letters are arranged together

Quantity B

The probability that all the same consonant letters are arranged together


There are 20 students in class with 10 girls and 10 boys. A teacher randomly selects some students and the first 6 students are all girls.

Quantity A

The probability that the 7th student is a girl

Quantity B

$$\frac{2}{7}$$


In a box of 10 electrical parts, 2 are defective. If someone selects 2 electrical parts randomly, what is the probability that neither of the parts will be defective?
Give your answer as a fraction.
How many positive divisors of 16 are multiples of 3?
The room number is between 200 and 999, inclusive. If the double room has the unit digit of 3,what's the ratio of the number of double room to all the room?
Give your answer as a fraction.
When randomly selecting 2 balls out of a box of 6 red balls and 10 blue balls, what is the probability that 1 red ball and 1 blue ball are selected at the same time? fraction.
If someone selects two numbers from 5,8,9,9,9 without replacement, what is the probability that the sum of the two numbers is multiple of 3?
Give your answer as afraction.
Select two numbers simultaneously from 1, 2, 3, 4, 5, what is the probability that the product of two numbers is odd?
Give your answer as a fraction.
4 out of 10 people are majored in mathematics. If you want to choose a team of 3 people out of these 10 people, what is the probability that there are at least 2 mathematics professionals in this team?
There are 12 bags of spice, which includes 5 different flavors. Among these, one bag`s flavor is C and 5 bags is of cherry flavor. What is the probability that one C flavor and one cherry flavor are drawn out when someone draw two bags of spice from the 12 bags?
Give your answer as a fraction.

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