A complete guide to Permutation, Combination and Probability. All you need for GMAT

[lego2401]

Originally Posted by dadaruh

Hey, since I recognized the answer you have given to Lego's similar question, i got the way you answered to #3. However, regarding the question, I thought that none-blue can be found if we dare to find the all-of-them-blues and subtract from 1. It seems wrong approach but, could you give a reason?


i appriciate.

ugur

You could have also used the 1-Blue approach, although as twin said, its long.

I think you missed on one of the possible outcomes.

We have 2 BLUE or 1 BLUE

in the case of two blue, its simply
2/8 * 1/7 = 1/28

In the second case, one blue and one not, you must have considered:

2/8*6/7 = 6/28.

But you didnt consider it the other way around, where the FIRST is not blue and the second is blue,

6/8 * 2/7 = 6/28

so adding them up, we get 13/28

So 1- 13/28 = 15/28

Hope that helps.......

[haneen97]

Can someone please explain how to solve this problem?

At a certain business school, 400 students are members of the sailing club, the wine club, or both. If 200 students are members of the wine club and 50 students are members of both clubs, what is the probability that a student chosen at random is a member of the sailing club?



A. 1/2

B. 5/8

C. 1/4

D. 3/8

E. 3/5

Thanks

[TwinnSplitter]

Total Students = Sailing Club + Wine Club - Both

400 = (Sailing Club) + 200 - 50

Sailing Club = 250

Probability of choosing someone who is in the sailing club
= (Sailing Club) / (Total)
= 250 / 400
= 5/8

B

[haneen97]

Thank you.

I made an error trying to calculate the Saling club members.

[Weekender]

wow!!! this post was really helpful to understand probability better...thanks you guys

[poundgmat]

Dudes,



Try this.. You were missing a piece of the url

http://www.mansw.nsw.edu.au/members/...ol23no4yen.htm

- HAVE FUN!!

Very useful.... I recommend downloading that probability.doc as well..

Originally Posted by lego2401

Yeah it is, I just tried it.

[piggylum]

Guys,

U can go to this site, I found the concept easier and plenty of useful
examples!

http://www.mansw.nsw.edu.au/members/...no1_larkin.htm


Permutation, Combination and probability

[first knight]

A certain deck of cards contains 2 blue cards, 2 red cards, 2 yellow cards, and 2 green cards. If two cards are randomly drawn from the deck, what is the probability that they will both are not blue?



A. 15/28

B. 1/4

C. 9/16

D. 1/32

E. 1/16

At a certain business school, 400 students are members of the sailing club, the wine club, or both. If 200 students are members of the wine club and 50 students are members of both clubs, what is the probability that a student chosen at random is a member of the sailing club?



A. 1/2

B. 5/8

C. 1/4

D. 3/8

E. 3/5

Thanks!

[Ankost]

1.A.
What is the probability that cards will both are not blue?
Total number of catds, which are not blue 6. They are randomly drawn from the deck. One card is drawn, 5 not blue cards left.
(6/8)*(5/7)=15/28

2. B.
To find members of sailing club x
200+x-50=400
x=250
250/400=5/8

[almas]

[quote=TwinnSplitter]Thanks for these great resources.

My answers to that document are as follows, anybody else who did them let me know what you got:
B
C
A
C

A bag of 10 marbles contains 3 red marbles and 7 blue marbles. If two marbles are selected at random, what is the probability that at least one marble is blue?

D (the way I did this took kind of long, if somebody else could let me know how they did it I'd appreciate it)


(7c1*3c1+7c2)10c2= 42/45=14/15
answer D