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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

First the inequality simplifies to x <= 20. 1/4x - 5 <=0 1/4x <= 5 4*(1/4x) <= 4*5 x <= 20

We need to know what the options are in set T before we know the probability of selecting a value for x that is <= 20.

vksunder wrote:

If x is to be selected at random from T, what is the probability that 1/4x - 5 <=0?

1. T is a set of 8 integers This doesn't give us enough information. We know the total number, but all numbers in Set T could be greater than 20 thus giving us probability of 0, or they could all be less than 20 giving us a probability of 1, or anything in between. INSUFFICIENT 2. T is contained in the set of integers from 1 to 25, inclusive INSUFFICIENT. We need to know how many of the integers in the set of integers from 1 to 25 make up T. since we do not know this, we do not know the total number of integers in the pool, and since some integers are higher than 20, some will satisfy the inequality and others will not. Once we know how many integers we would need to know which ones make up T.

TOGETHER: Insufficient. Together we know that T consists of 8 integers from 1 to 25, but because we could have all that are <= 20 and probability would be 1, or we could include any number of integers from 21 to 25 inclusive thus giving us many different probability values.

_________________

------------------------------------ J Allen Morris **I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

If x is to be selected at random from T, what is the probability that 1/4x - 5 <=0?

1. T is a set of 8 integers 2. T is contained in the set of integers from 1 to 25, inclusive

1/4x - 5 <=0 x<=20 1) T is a set of 8 integers Can be any 8 integers >20 or can be any integers <20..

insuffcient. 2) {1,2,...25}

probablity = 20/25

B is the answer.

I defininetly agree with you however OA is E,

it is written from 1 to 25 so it means t= (1,2,3,4...23,24,25) why it is not B couldnt understand...

Bunuel Can you check and help us plz?

First of all: 1/4x - 5 <=0 should be written as 1/4*x - 5 <=0.

1. If x is to be selected at random from T, what is the probability that \(\frac{1}{4}*x-5\leq{0}\)?

\(\frac{1}{4}*x-5\leq{0}\) --> is \(x\leq{20}\)?

(1) T is a set of 8 integers. Clearly insufficient. (2) T is contained in the set of integers from 1 to 25, inclusive. Though the wording is a little bit strange but it means that set T is a subset of a set of integers from 1 to 25, inclusive. Set T can be {1,5,7} or {21,22,25}... Also insufficient.

(1)+(2) T can be set of 8 integers, which are ALL less than or equal to 20 and in this case \(P(x\leq{20})=1\) or T can be set of 8 integers which are NOT ALL all less than or equal to 20 and in this case \(P(x\leq{20})<1\). Not sufficient.

Answer: E.

You should spotted that there was something wrong with your approach as (1) say that T is a set of 8 integers and if (2) says that T is a set of integers from 1 to 25 inclusive, so set of 25 integers (as you suggested) then it would mean that statements contradict each other and on GMAT two statements never contradict.

This is why I like the contradiction, one statement can hint at the parameters or bounds. If I had looked at statement 2 first, I probably would have forgotten about the limit that the number of the set is not yet defined. But you look at the other statement, and see they limit the set to 8 digits, and it sets off a lightbulb in my head. If the set had 1 number or 25 numbers, would give different answers.
_________________

If you liked my post, please consider thanking me with Kudos! I really appreciate it!

If x is to be selected at random from T, what is the probability that 1/4x - 5 <=0? x<= 20

1. T is a set of 8 integers 2. T is contained in the set of integers from 1 to 25, inclusive

St.1 [IS] set of the same integers? integers less than 20? negative integers? St.2 [IS] 1-25 inclusive maybe all the integers are the same no. 25 or no. 10

With both, you can conclude that there is a set of 8 integers between the no. 1-25 inclusive. They can still be all the same integers or all int less than 20 or all int greater than 20 or consist of random proportion of int greater/less than 20. Therefore you can not conclude a definite answer so ---> (E)

f x is to be selected at random from T, what is the probability that 1/4x - 5 <=0?

First of all: 1/4x - 5 <=0 should be written as 1/4*x - 5 <=0.

1. If x is to be selected at random from T, what is the probability that \(\frac{1}{4}*x-5\leq{0}\)?

\(\frac{1}{4}*x-5\leq{0}\) --> is \(x\leq{20}\)?

(1) T is a set of 8 integers. Clearly insufficient. (2) T is contained in the set of integers from 1 to 25, inclusive. Though the wording is a little bit strange but it means that set T is a subset of a set of integers from 1 to 25, inclusive. Set T can be {1,5,7} or {21,22,25}... Also insufficient.

(1)+(2) T can be set of 8 integers, which are ALL less than or equal to 20 and in this case \(P(x\leq{20})=1\) or T can be set of 8 integers which are NOT ALL all less than or equal to 20 and in this case \(P(x\leq{20})<1\). Not sufficient.

Answer: E.

You should spotted that there was something wrong with your approach as (1) say that T is a set of 8 integers and if (2) says that T is a set of integers from 1 to 25 inclusive, so set of 25 integers (as you suggested) then it would mean that statements contradict each other and on GMAT two statements never contradict.

Hope it's clear.

Bunuel,

Is it not possible to arrive at the answer by combining the two statements? Theoretically, we can identify all the subsets of 8 integers from 1 to 25, find the probability of X>=20 in all those subsets and add those probabilities.

f x is to be selected at random from T, what is the probability that 1/4x - 5 <=0?

First of all: 1/4x - 5 <=0 should be written as 1/4*x - 5 <=0.

1. If x is to be selected at random from T, what is the probability that \(\frac{1}{4}*x-5\leq{0}\)?

\(\frac{1}{4}*x-5\leq{0}\) --> is \(x\leq{20}\)?

(1) T is a set of 8 integers. Clearly insufficient. (2) T is contained in the set of integers from 1 to 25, inclusive. Though the wording is a little bit strange but it means that set T is a subset of a set of integers from 1 to 25, inclusive. Set T can be {1,5,7} or {21,22,25}... Also insufficient.

(1)+(2) T can be set of 8 integers, which are ALL less than or equal to 20 and in this case \(P(x\leq{20})=1\) or T can be set of 8 integers which are NOT ALL all less than or equal to 20 and in this case \(P(x\leq{20})<1\). Not sufficient.

Answer: E.

You should spotted that there was something wrong with your approach as (1) say that T is a set of 8 integers and if (2) says that T is a set of integers from 1 to 25 inclusive, so set of 25 integers (as you suggested) then it would mean that statements contradict each other and on GMAT two statements never contradict.

Hope it's clear.

Bunuel,

Is it not possible to arrive at the answer by combining the two statements? Theoretically, we can identify all the subsets of 8 integers from 1 to 25, find the probability of X>=20 in all those subsets and add those probabilities.

What is wrong in my approach here?

Thank you.

When a DS question asks to find some value, then the statement is sufficient ONLY if you can get the single numerical value.

Since we cannot get the single numerical value of the probability alsed, thee the answer is E.

If x is to be selected at random from T, what is the probabi [#permalink]

Show Tags

02 Jul 2014, 17:25

Bunuel wrote:

keenys wrote:

Bunuel wrote:

f x is to be selected at random from T, what is the probability that 1/4x - 5 <=0?

First of all: 1/4x - 5 <=0 should be written as 1/4*x - 5 <=0.

1. If x is to be selected at random from T, what is the probability that \(\frac{1}{4}*x-5\leq{0}\)?

\(\frac{1}{4}*x-5\leq{0}\) --> is \(x\leq{20}\)?

(1) T is a set of 8 integers. Clearly insufficient. (2) T is contained in the set of integers from 1 to 25, inclusive. Though the wording is a little bit strange but it means that set T is a subset of a set of integers from 1 to 25, inclusive. Set T can be {1,5,7} or {21,22,25}... Also insufficient.

(1)+(2) T can be set of 8 integers, which are ALL less than or equal to 20 and in this case \(P(x\leq{20})=1\) or T can be set of 8 integers which are NOT ALL all less than or equal to 20 and in this case \(P(x\leq{20})<1\). Not sufficient.

Answer: E.

You should spotted that there was something wrong with your approach as (1) say that T is a set of 8 integers and if (2) says that T is a set of integers from 1 to 25 inclusive, so set of 25 integers (as you suggested) then it would mean that statements contradict each other and on GMAT two statements never contradict.

Hope it's clear.

Bunuel,

Is it not possible to arrive at the answer by combining the two statements? Theoretically, we can identify all the subsets of 8 integers from 1 to 25, find the probability of X>=20 in all those subsets and add those probabilities.

What is wrong in my approach here?

Thank you.

When a DS question asks to find some value, then the statement is sufficient ONLY if you can get the single numerical value.

Since we cannot get the single numerical value of the probability alsed, thee the answer is E.

Hope it's clear.

Bunuel,

I find myself in the same position as Keenys'.

Won't we get a single numerical value though if we do identify all the subsets and add all those "OR" possibilities?

Or the reason why this approach is wrong is that the question asks us for the probability of getting an x from a subset T that is supposed to be "fixed," not variable? And for this reason, we cannot get a single numerical value since we can have multiple possibilities for the subset T?

Won't we get a single numerical value though if we do identify all the subsets and add all those "OR" possibilities?

Or the reason why this approach is wrong is that the question asks us for the probability of getting an x from a subset T that is supposed to be "fixed," not variable? And for this reason, we cannot get a single numerical value since we can have multiple possibilities for the subset T?

Thank you.

I don't think it is possible to arrive at single answer with the information given by the statements.

Both statements together tell us that T is a subset of 8 integers of superset of 25 integers starting from 1 to 25

So we can easily create a few subsets of 8 integers that give is different probabilities. Subset 1 -------> 1,2,3,4,5,6,7,8 ---------> Probability of x being <= 20 is 1 Subset 2 --------> 1,2,8,10,21,22,24,25 -------> Probability of x being <= 20 is 0.5 Subset 3 --------> 25,25,25,25,25,25,25,25 --------> Probability of x being <= 20 is 0 (Note that we are not told that the integers in set of 8 integers are all distinct)
_________________

Re: If x is to be selected at random from T, what is the probabi [#permalink]

Show Tags

26 Feb 2016, 12:18

Hello from the GMAT Club BumpBot!

Thanks to another GMAT 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.
_________________

There’s something in Pacific North West that you cannot find anywhere else. The atmosphere and scenic nature are next to none, with mountains on one side and ocean on...

This month I got selected by Stanford GSB to be included in “Best & Brightest, Class of 2017” by Poets & Quants. Besides feeling honored for being part of...

Joe Navarro is an ex FBI agent who was a founding member of the FBI’s Behavioural Analysis Program. He was a body language expert who he used his ability to successfully...