Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 29 May 2017, 05:53

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# There are five different pairs of boots in the box. Find the

Author Message
VP
Joined: 08 Jun 2005
Posts: 1145
Followers: 7

Kudos [?]: 213 [0], given: 0

There are five different pairs of boots in the box. Find the [#permalink]

### Show Tags

02 Oct 2007, 11:10
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

There are five different pairs of boots in the box. Find the probability of two boots being pulled of the box at random are of the same pair?

1*1/9 = 1/9

first - any boot 10/10 = 1

second - his pair out of nine boots = 1/9

VP
Joined: 08 Jun 2005
Posts: 1145
Followers: 7

Kudos [?]: 213 [0], given: 0

### Show Tags

02 Oct 2007, 11:15
What is the probability og two books being standing in adjacent places in a row of ten different books?

(9!*2)/10! = 1/5

9!*2 = ways to arrange ten books when two books together AB & BA hence multiply by two.

10! = ways to arrange ten books.

Director
Joined: 17 Sep 2005
Posts: 906
Followers: 4

Kudos [?]: 78 [0], given: 0

### Show Tags

02 Oct 2007, 13:11
OlgaN wrote:
1.There are five different pairs of boots in the box. Find the probability of two boots being pulled of the box at random are of the same pair?

A 1\10
B 1\45
C 1\90
D 1\9
E 3\20

Total No of boots = 2*5 = 10
No of ways of selecting 1 pair out of 5 pairs = 5C1 = 5
Total No of ways of selecting 2 boots out of 10 boots = 10C2 = 45

So Probability of selecting two boots of same pair = 5/45 = 1/9

Hence D.

- Brajesh
Director
Joined: 18 Jul 2006
Posts: 526
Followers: 1

Kudos [?]: 59 [0], given: 0

### Show Tags

02 Oct 2007, 13:13
OlgaN wrote:
1.There are five different pairs of boots in the box. Find the probability of two boots being pulled of the box at random are of the same pair?

A 1\10
B 1\45
C 1\90
D 1\9
E 3\20

Take any one boot out. Now out of 9 boots, there is only one which will form pair.
Prob = 1/9
Director
Joined: 17 Sep 2005
Posts: 906
Followers: 4

Kudos [?]: 78 [0], given: 0

### Show Tags

02 Oct 2007, 13:15
OlgaN wrote:
2.What is the probability og two books being standing in adjacent places in a row of ten different books?

A 1\10
B 1\5
C 1\100
D 1\9
E 2\45

Thanks.

There are 10 books.
We can arrange total of 10 books in 10! ways.

Now, 2 books adjacent to each other can be arranged in 2 ways.
2 books together and rest of 8 books can be arranged in 9! ways.

Therefore total no of favourable ways of arrangement = 2 * 9!
Total ways of arrangement = 10!

So Required probability = 2*9!/10! = 2/10 = 1/5

Hence, B.

- Brajesh
Re: Probability PS   [#permalink] 02 Oct 2007, 13:15
Display posts from previous: Sort by