37 Answered Questions for the topic Combinatorics

06/26/19

Test preparation

A class is given 20 study problems from which 10 will be part of the exam. Student knows how to solve 15 of them. What are the chances that he will correctly answer:a) all 10b) exactly 8c) at least 9

04/12/19

GRE quant question (hard)?

"I got this question from the GRE book. Central state college has three sections of Math 102. If four students, Bill, Jill, Phill, and Will decide to transfer from Math 101 into Math 102, in how... more

03/23/19

Is the Maclaurin series expansion of $\\sin x$ related to the inclusion-exclusion principle?

When I see the alternating signs in the infinite series expansion of $\\sin x$, I'm reminded of the inclusion-exclusion principle. Could there be any way to visualize it in such a way? Also, is... more

03/19/19

Intuition behind combination problem?

I came across this question on a GRE practice exam. I'm trying to build intuition behind how to correctly approach these types of problems: A reading list for a humanities course consists of 10... more

03/15/19

Combination GRE problem 25?

An appliance's model number consists of three alphanumeric characters. The first character must be one of 24 permissible letters of the alphabet. The next character is numeric, a digit from 1 to 9.... more

03/13/19

Intuition behind combination problem?

I came across this question on a GRE practice exam. I'm trying to build intuition behind how to correctly approach these types of problems: A reading list for a humanities course consists of 10... more

03/13/19

combination gre problem # 24?

How many ways can 4 prizes be given away to 3 boys, if each boy is eligible for all the prizes? Can anyone explain me why this answer is wrong: 4*4*4 ?

03/13/19

Is the Maclaurin series expansion of $\\sin x$ related to the inclusion-exclusion principle?

When I see the alternating signs in the infinite series expansion of $\\sin x$, I'm reminded of the inclusion-exclusion principle. Could there be any way to visualize it in such a way? Also, is... more

12/15/18

Probability and combinatorics questions

If there are 20 people with 17 men and 3 women and they seat themselves randomly at 4 Tables (A,B,C,D) with 5 people each. With all arrangements being equally likely, what is the probability that... more

12/15/18

Probability and combinatorics questions

If there are 20 people with 17 men and 3 women and they seat themselves randomly at 4 Tables (A,B,C,D) with 5 people each. With all arrangements being equally likely, what is the probability that... more

10/06/18

11 different people and 11 rank places, how many distinct rank lists are possible with different rank places for every person?

11 different people and 11 rank places, how many distinct rank lists are possible with different rank places for every person?

06/23/18

You have 7 shirt and 4 ties. How many shirt-tie outfits can you make?

I need help answering this question .

06/02/18

Number arranging

The number of ways of arranging the 26 letters of the English alphabet = 26!. If a computer prints these arrangements at the rate of 1000 per second, how long will this take?

05/27/18

How many ways can I park 5 cars?

I have 5 cars (a BMW, a Chevy, a Fiat, a Honda, and a Kia) and 8 parking lots. How many ways can I distribute these over the available slots?   I thought the solution to the problem was simply... more

05/26/18

Probability of winning raffle with multiple tickets (max one win each)

I have 90 tickets in a raffle.20,000 people have bought tickets.Each person has bought between between 60 and 100 tickets.The total number of tickets sold is 1,360,000 giving an average of 68... more

05/26/18

Determine the total number of ways...

Three students were selected from 23 senior students to be president, vice-president, and secretary of the student council. Three other students from 38 sophomore and junior students were also... more

05/24/18

Confusing combinatorics problem

A 4x5 grid has points A and C on opposite corners of the grid. Point B is 4 units east and 1 south from point A.   If the only allowed directions are south and east, what is the number of... more

05/25/17

Counting Two Pair 5-card Poker Hands

I'm trying to understand combinatorics and I'm having some trouble with the popular 'Two Pairs' problem. The question asks how many Two Pair hands can be made from a deck of 52.   I know the... more

05/14/17

Probability of Getting a Test Question Correct Given Studying Some of the Possible Questions

A class is given a list of 20 study questions from which 12 will be part of their upcoming final. If a given student knows how to solve 15 of the problems, find the probability that the student... more

10/30/16

combination question

An equal number of juniors and seniors are trying out for six spots on the university debating team. If the team must consist of at least four seniors, then how many different possible debating... more

10/11/16

combinatorics and probability

A committee of 6 people is chosen from 8 women and 8 men. How many different committees are possible that consists of 3 women and 3  men ?

10/11/16

combinatorics and probability

SEVEN DISTINCT POINTS ARE DRAWN ON A CIRCLE. HOW MANY DIFFERENT TRIANGLES CAN BE DRAWN IN WHICH EACH VERTEX OF THE TRIANGLE IS AT 1 OF THE 7 POINTS?

07/05/16

Combinatorics in a Poker Hand

Let's say I make a big bet in a poker game.  I have 2 other opponents in the hand.  One opponent will call me 8% of the time.  The second opponent calls 10% (let's just assume for simplicity that... more
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