Last visit was: 21 Nov 2024, 15:47 It is currently 21 Nov 2024, 15:47

Close

GRE Prep 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 GRE 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
User avatar
Retired Moderator
Joined: 07 Jun 2014
Posts: 4812
Own Kudos [?]: 11189 [4]
Given Kudos: 0
GRE 1: Q167 V156
WE:Business Development (Energy and Utilities)
Send PM
Most Helpful Community Reply
avatar
Manager
Manager
Joined: 27 Feb 2017
Posts: 188
Own Kudos [?]: 148 [8]
Given Kudos: 0
Send PM
General Discussion
Retired Moderator
Joined: 07 Jan 2018
Posts: 739
Own Kudos [?]: 1447 [1]
Given Kudos: 93
Send PM
User avatar
Retired Moderator
Joined: 07 Jun 2014
Posts: 4812
Own Kudos [?]: 11189 [0]
Given Kudos: 0
GRE 1: Q167 V156
WE:Business Development (Energy and Utilities)
Send PM
Re: Jan and 5 other children are in a classroom. The principal o [#permalink]
1
Expert Reply
Explanation

The probability of any event equals the number of ways to get the desired outcome divided by the total number of outcomes.

Start with the denominator, which is the total number of ways that the principal can choose two children from the classroom. Use the fundamental counting principle. There are 6 possible options for the first choice and 5 for the second, giving (6)(5) = 30 possibilities.

However, this double-counts some cases; for example, choosing Jan and then Robert is the same as choosing Robert and then Jan.

Divide the total number of pairs by 2: \(\frac{6 \times 5}{2}= 1\). Alternatively, use the formula for a set in which the order doesn’t matter: \(\frac{total!}{in! \times out!}\).

In this case: \(\frac{6!}{2! \times 4!}=15\).

Now compute the numerator, which is the number of pairs that include Jan. Since the pair only includes two children and one is already decided (Jan), there are exactly 5 options for the other child. Thus, there are 5 total pairs that include Jan: Jan with each of the other students.

The probability of choosing a pair with Jan is \(\frac{1}{3}\).
User avatar
Manager
Manager
Joined: 01 Nov 2018
Posts: 87
Own Kudos [?]: 144 [1]
Given Kudos: 0
Send PM
Re: Jan and 5 other children are in a classroom. The principal o [#permalink]
1
Expert Reply
kruttikaaggarwal wrote:
Is this method right?

Probablility of Jan not being chosen: 5/6 *4/5=4/6=2/3
Probability of Jan being chosen = 1 - 2/3=1/3




Yes! much simpler too! Thanks !!
Manager
Manager
Joined: 23 May 2021
Posts: 146
Own Kudos [?]: 45 [0]
Given Kudos: 23
Send PM
Re: Jan and 5 other children are in a classroom. The principal o [#permalink]
I am a bit confused at times, when do u know if the order matters and when u know it dosent matter?
Verbal Expert
Joined: 18 Apr 2015
Posts: 30003
Own Kudos [?]: 36337 [0]
Given Kudos: 25927
Send PM
Re: Jan and 5 other children are in a classroom. The principal o [#permalink]
Expert Reply
aishumurali wrote:
I am a bit confused at times, when do u know if the order matters and when u know it dosent matter?


Frankly I am confused too....but on how we work so hard to help and provide the students with top notch resources to achieve the best score. No room for unclear or lack of tool

https://gre.myprepclub.com/forum/gre-quant ... 18819.html

Just reading and absorbing is that simple
User avatar
GRE Prep Club Legend
GRE Prep Club Legend
Joined: 07 Jan 2021
Posts: 5030
Own Kudos [?]: 74 [0]
Given Kudos: 0
Send PM
Re: Jan and 5 other children are in a classroom. The principal o [#permalink]
Hello from the GRE Prep Club BumpBot!

Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Prep Club for GRE Bot
Re: Jan and 5 other children are in a classroom. The principal o [#permalink]
Moderators:
GRE Instructor
84 posts
GRE Forum Moderator
37 posts
Moderator
1111 posts
GRE Instructor
234 posts

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