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mmelendez
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What does s^2t-st^2 equal given that s and t are positive integ Updated on: 13 Nov 2015, 16:21
Originally posted by mmelendez on 13 Nov 2015, 15:54.
Last edited by ENGRTOMBA2018 on 13 Nov 2015, 16:21, edited 3 times in total.
Reformatted the question
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55% (hard)

Question Stats:

57% (01:39) correct 43% (01:47) wrong based on 164 sessions

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What does \(s^2t-st^2\) equal given that s and t are positive integer, both are greater than 1 and t<s?

Statement 1, t is a prime integer
Statement 2, st=15

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B
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ENGRTOMBA2018
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What does s^2t-st^2 equal given that s and t are positive integ 13 Nov 2015, 16:09
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mmelendez
Given s and t are integers greater than 1 and t<s, what is the value of \(s^2t-st^2\) ?

Statement 1, \(t\) is a prime number
Statement 2, \(st=15\)


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Please follow posting guidelines (link in my signatures) or else I will have to delete the question. No emoticons or unnecessary text in the question. Topic should be a lot more than first 2-3 words.

Your original question talked about s and t being greater than and then you mention they are greater than 1 as well. It only needs to mention that both s,t are >1.

Also, prime can ONLY be integers and as such mentioning both in statement 1 is redundant. GMAT language is a lot more subtle and to the point.

As for this question,

\(s^2t-st^2\) = ? with s and t \(\in\) integers > 1.

Per statement 1, t= prime number . Too many options for t and no clue about s, making this statement not sufficient.

Per statement 2, st=15 ---> as both s and t>1 and 15 has 1,3,5,15 as the factors, only (3,5) or (5,3) will work as (s,t) pair. But it is also given that s>t and thus (3,5) is eliminated , giving us the only possible values of s,t as 5,3 and hence you will get a unique value of \(s^2t-st^2\) (no need to solve this final unique value).
This statement is sufficient.

B is the correct answer.
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What does s^2t-st^2 equal given that s and t are positive integ 13 Nov 2015, 16:17
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Actually I am coping and pasting the question as exactly as it looks from the gmat course provider.
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ENGRTOMBA2018
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What does s^2t-st^2 equal given that s and t are positive integ 13 Nov 2015, 16:20
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mmelendez
Actually I am coping and pasting the question as exactly as it looks from the gmat course provider.
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Ok so this only goes to show that you need to mention your source in the questions you post if you select the tag "Source-others please specify" because some sources are notoriously average. GMAT language is very clear and only a handful of companies are good at producing good quality questions.

I have reverted back to the original language.
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What does s^2t-st^2 equal given that s and t are positive integ 13 Nov 2015, 16:28
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I think the purpose of them having such questions is to train students to sort out information and extract only the most important details, as business managers must do in the real world.

My idea is to share those so that I can stir discussion on quality, method of reasoning, solutions and skills applications
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What does s^2t-st^2 equal given that s and t are positive integ 13 Nov 2015, 16:30
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mmelendez
I think the purpose of them having such questions is to train students to sort out information and extract only the most important details, as business managers must do in the real world.

My idea is to share those so that I can stir discussion on quality, method of reasoning, solutions and skills applications
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Ok. Good point. I have updated the question again to your original post.
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What does s^2t-st^2 equal given that s and t are positive integ 30 Jun 2024, 05:53
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