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# If x is to be selected at random from T, what is the

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If x is to be selected at random from T, what is the [#permalink]  18 Aug 2008, 12:17
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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
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Re: DS: probability [#permalink]  18 Aug 2008, 12:35
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
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

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Re: DS: probability [#permalink]  18 Aug 2008, 13:14
i think B ; the probability would be 1
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Re: DS: probability [#permalink]  18 Aug 2008, 14:11
stallone wrote:
i think B ; the probability would be 1

What if select 24.. check it.

1/4 x - 5 <=0 --> 1/4 * 24 -5<=0 ---> 6-5<=0 ----> 1<=0 is this correct??????
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Re: DS: probability [#permalink]  18 Aug 2008, 14:26
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I think the answer is E.

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.

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**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$. Find out what's new at GMAT Club - latest features and updates Intern Joined: 17 Aug 2008 Posts: 21 Followers: 0 Kudos [?]: 0 [0], given: 0 Re: DS: probability [#permalink] 18 Aug 2008, 15:23 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 Simplifying the question, we get, x<=20; From the choices, can we find if x<=20? Choice 1: No Choice 2: No Combined: No So, the answer is E. Director Joined: 12 Jul 2008 Posts: 523 Schools: Wharton Followers: 11 Kudos [?]: 72 [0], given: 0 Re: DS: probability [#permalink] 20 Aug 2008, 04:29 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 2. T is contained in the set of integers from 1 to 25, inclusive E. (1) Insufficient Could be any set of 8 integers. Tells us nothing. (2) Insufficient Does not tell us how many and/or what numbers comprise T. T could = {1,2,3,4), where probability = 1 T could = {1,2,3,25}, where probability = 3/4 (1) and (2) Insufficient Tells us how many integers are in T but does not tells us which integers are in T. SVP Joined: 07 Nov 2007 Posts: 1841 Location: New York Followers: 20 Kudos [?]: 292 [0], given: 5 Re: DS: probability [#permalink] 20 Aug 2008, 06:46 zoinnk wrote: 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 2. T is contained in the set of integers from 1 to 25, inclusive E. (1) Insufficient Could be any set of 8 integers. Tells us nothing. (2) Insufficient Does not tell us how many and/or what numbers comprise T. T could = {1,2,3,4), where probability = 1 T could = {1,2,3,25}, where probability = 3/4 (1) and (2) Insufficient Tells us how many integers are in T but does not tells us which integers are in T. Thanks everyone.. I agree with E 2. T is contained in the set of integers from 1 to 25, inclusive I missed the highlighted part. _________________ Your attitude determines your altitude Smiling wins more friends than frowning SVP Joined: 30 Apr 2008 Posts: 1900 Location: Oklahoma City Schools: Hard Knocks Followers: 25 Kudos [?]: 341 [0], given: 32 Re: DS: probability [#permalink] 20 Aug 2008, 06:48 Are you forgetting my 5 steps to DS success? x2suresh wrote: zoinnk wrote: 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 2. T is contained in the set of integers from 1 to 25, inclusive E. (1) Insufficient Could be any set of 8 integers. Tells us nothing. (2) Insufficient Does not tell us how many and/or what numbers comprise T. T could = {1,2,3,4), where probability = 1 T could = {1,2,3,25}, where probability = 3/4 (1) and (2) Insufficient Tells us how many integers are in T but does not tells us which integers are in T. Thanks everyone.. I agree with E 2. T is contained in the set of integers from 1 to 25, inclusive I missed the highlighted part. _________________ ------------------------------------ J Allen Morris **I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

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Re: DS: probability [#permalink]  20 Aug 2008, 06:54
jallenmorris wrote:
Are you forgetting my 5 steps to DS success?

From last week my mind is rotating.. No proper sleep.. Busy with work.. no time man..!!! Killing..

I Forgot Major step to Success : Step (A) Sleep well, do well..
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Re: DS: probability [#permalink]  21 Aug 2008, 19:13
Thanks for the wonderful explanation guys! OA=E.

Allen - what are the 5 magic steps?
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Re: DS: probability [#permalink]  20 Aug 2010, 02:46
x2suresh wrote:
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
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

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?
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Re: DS: probability [#permalink]  20 Aug 2010, 06:34
fatihaysu wrote:
x2suresh wrote:
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
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

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.

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.
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Re: DS: probability [#permalink]  20 Aug 2010, 06:43
Good tip about contradiction bunuel, whatever I asked you,you are perfect on it buddy I think you should write a book,

If you don't mind What was your GMAT score?
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Re: DS: probability [#permalink]  20 Aug 2010, 21:39
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.
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Re: DS: probability [#permalink]  06 Jan 2011, 11:11
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)
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Re: DS: probability [#permalink]  11 Jan 2011, 18:52
some people (like myself) thought that 1/4x is 1/(4x). In this case B is the answer with a probability of 1. Otherwise the answer is E
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X is to be selectced [#permalink]  21 Feb 2011, 10:05
114) if x is to be selected at random from set 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.
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Re: X is to be selectced [#permalink]  21 Feb 2011, 10:13
Merging similar topics.

GMATD11 wrote:
114) if x is to be selected at random from set 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.

Please format the questions properly. In order E to be the answer question should read: "what is the probability that 1/4*x-5<=0[/color]?"
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Re: DS: probability [#permalink]  22 Feb 2011, 14:48
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

Does any one else think the question itself is not standard: in a DS question "What is the probability that " sounds like PS.

Can you point me to any other questions ?
Re: DS: probability   [#permalink] 22 Feb 2011, 14:48
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