It is currently 20 Oct 2017, 23:58

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Senior Manager
Senior Manager
avatar
G
Joined: 26 Dec 2015
Posts: 254

Kudos [?]: 52 [0], given: 1

Location: United States (CA)
Concentration: Finance, Strategy
WE: Investment Banking (Venture Capital)
If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen [#permalink]

Show Tags

New post 18 Aug 2017, 09:24
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

74% (00:30) correct 26% (00:31) wrong based on 66 sessions

HideShow timer Statistics

If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen randomly from the set {20, 21, 22, 23}, what is the probability that both x and y are prime numbers?

A) \(\frac{1}{5}\)

B) \(\frac{3}{20}\)

C) \(\frac{13}{20}\)

D) \(\frac{3}{10}\)

E) \(\frac{1}{10}\)
[Reveal] Spoiler: OA

Kudos [?]: 52 [0], given: 1

Manager
Manager
User avatar
S
Joined: 22 May 2015
Posts: 74

Kudos [?]: 15 [0], given: 22

Re: If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen [#permalink]

Show Tags

New post 18 Aug 2017, 09:31
Gng back to basics

Probability = No of Favorable Outcomes / total no of Outcomes

Total No of Outcomes = 5C1 * 4C1
No of Favorable Outcomes = 2 * 1

=> Probability = 1/10
_________________

Consistency is the Key

Kudos [?]: 15 [0], given: 22

Senior Manager
Senior Manager
avatar
G
Joined: 25 Feb 2013
Posts: 417

Kudos [?]: 183 [0], given: 31

Location: India
GPA: 3.82
GMAT ToolKit User Reviews Badge
Re: If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen [#permalink]

Show Tags

New post 18 Aug 2017, 12:15
LakerFan24 wrote:
If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen randomly from the set {20, 21, 22, 23}, what is the probability that both x and y are prime numbers?

A) \(\frac{1}{5}\)

B) \(\frac{3}{20}\)

C) \(\frac{13}{20}\)

D) \(\frac{3}{10}\)

E) \(\frac{1}{10}\)


For \(x\) there are 2 prime nos available in the set of 5 integers {\(7,11\)}. Hence Probability of \(x\) being prime \(= \frac{2}{5}\)
For \(y\) there is 1 prime no. available in the set of 4 integers {\(23\)}. Hence Probability of \(y\) being prime \(= \frac{1}{4}\)
So Probability of \(x AND y\) being prime \(= \frac{2}{5}*\frac{1}{4} = \frac{1}{10}\)
Option E

Kudos [?]: 183 [0], given: 31

Manager
Manager
User avatar
S
Joined: 27 Dec 2016
Posts: 154

Kudos [?]: 38 [0], given: 192

Concentration: Social Entrepreneurship, Nonprofit
GPA: 3.65
WE: Sales (Consumer Products)
Premium Member CAT Tests
If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen [#permalink]

Show Tags

New post 19 Aug 2017, 21:54
1
This post was
BOOKMARKED
LakerFan24 wrote:
If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen randomly from the set {20, 21, 22, 23}, what is the probability that both x and y are prime numbers?

A) \(\frac{1}{5}\)

B) \(\frac{3}{20}\)

C) \(\frac{13}{20}\)

D) \(\frac{3}{10}\)

E) \(\frac{1}{10}\)


This is AND question - so we must MULTIPLY each probability.
1. P (X is prime) = \(\frac{possibilites that X are prime}{total number in the set}\) = \(\frac{2}{5}\). Only 7 and 11 are prime.
2. P (Y is prime) = \(\frac{possibilites that Y are prime}{total number in the set}\) = \(\frac{1}{4}\). Only 23 is prime.
3. P (X is prime AND y is prime) = \(\frac{2}{5}\) * \(\frac{1}{4}\) = \(\frac{2}{20}\)

E.
_________________

There's an app for that - Steve Jobs.

Kudos [?]: 38 [0], given: 192

If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen   [#permalink] 19 Aug 2017, 21:54
Display posts from previous: Sort by

If x is chosen randomly from the set {7, 8, 9, 10, 11} and y is chosen

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.