Punch of the Day (26/11/08)

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Sureshbala

Punch of the Day (26/11/08)

Author: Sureshbala

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What is "Punch Of The Day"?

Everyday Learnhub's team will post one question each on Verbal Ability and Quantitative Ability of the GMAT Test Preparation
Members can post their answers along with explanations for the next 24 hours.
After 24 hours, Learnhub's team will post the official answer along with the explanation.Besides answering the previous day's questions, Learnhub's Team will come up with the next set of questions for that day as well.

What are the rules of "Punch Of The Day"?

	Every user must refrain from posting sarcastic comments on the answers posted by others.
	Once the Learnhub's team posts the official answer along with the explanation, no comments must be made regarding those questions. In case of further clarification please send a personal message to the respective team member
	If you think that there is something wrong with the explanation of the Learnhub's Team, which seldom happens, please send a personal message to the respective team member informing him/her the same. Posting the same here will not be considered and will be deleted.
	Please bear in mind that only Learnhub's Team members have the privilege of posting questions here. Questions posted by other members will not be entertained and hence will be deleted immediately.

"Punch Of The Day" Team Members

Click here for the Previous Punch

Today's Punches

Punch 3: Sentence Correction

Tiny quantities of more than thirty rare gases, most of them industrial by-products, threaten to warm the Earth's atmosphere even more rapidly than carbon dioxide during the next fifty years

(A) to warm the Earth's atmosphere even more rapidly than carbon dioxide during the next fifty years
(B) to warm the Earth's atmosphere even more rapidly over the next fifty years than carbon dioxide will
(C) during the next fifty years to warm the Earth's atmosphere even more rapidly than carbon dioxide
(D) a warming of the Earth's atmosphere during the next fifty years even more rapid than carbon dioxide's.
(E) a warming of the Earth's atmosphere even more rapid than carbon dioxide's will be over the next fifty years

Punch 4: Data Sufficiency

The roots of a quadratic equation ax^2+bx+c=0

are integers and a+b+c>0 and a>0. Are both the roots of the equation positive?

Sum of the roots is positive.
Product of the roots is positive.

(A) Statement 1 alone is sufficient but statement 2 alone is not sufficient to answer the question asked.

(B) Statement 2 alone is sufficient but statement 1 alone is not sufficient to answer the question asked.

(C) Both statements 1 and 2 together are sufficient to answer the question but neither statement is sufficient alone.

(D) Each statement alone is sufficient to answer the question.

(E) Statements 1 and 2 are not sufficient to answer the question asked and additional data is needed to answer the statements.

Official answers will be posted tomorrow. Try to crack them before that….
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9 Comments

Blues said – Wed, 26 Nov 2008 17:17:20 -0000 ( Flag Edit Link )

A and E
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srao_ogirala said – Thu, 27 Nov 2008 06:31:34 -0000 ( Flag Edit Link )

B and C
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meagoenka said – Thu, 27 Nov 2008 08:10:52 -0000 ( Flag Edit Link )

A and C
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Reach high said – Thu, 27 Nov 2008 11:10:55 -0000 ( Flag Edit Link )

A and C
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Sureshbala said – Thu, 27 Nov 2008 16:18:03 -0000 ( Flag Edit Link )

Folks, here are the official answers

Punch 3: Sentence Correction

Tiny quantities of more than thirty rare gases, most of them industrial by-products, threaten to warm the Earth’s atmosphere even more rapidly than carbon dioxide during the next fifty years

(A) to warm the Earth’s atmosphere even more rapidly than carbon dioxide during the next fifty years
(B) to warm the Earth’s atmosphere even more rapidly over the next fifty years than carbon dioxide will
(C) during the next fifty years to warm the Earth’s atmosphere even more rapidly than carbon dioxide
(D) a warming of the Earth’s atmosphere during the next fifty years even more rapid than carbon dioxide’s.
(E) a warming of the Earth’s atmosphere even more rapid than carbon dioxide’s will be over the next fifty years

Explanation:
Notice that the subject of the clause is ‘TINY QUANTITIES (of more than thirty rare gases)” and has plural form. The verb that is used outside the underlined part is ‘threaten’ and is plural in form as required. In this example, the phrase ‘more than thirty rare gases’ that comes after the preposition ‘of’ is also plural and the verb is used clearly outside the underlined part for obvious reasons: even if you incorrectly considered the ‘object’ of the prepositional phrase as the subject, you would have still come up with a plural form of the verb.

Elimination of answer options must be done now on a consideration other than the match up of the subject and the verb. We notice the verb ‘threaten’ and the idiom requirement forces us to use the form ‘threaten TO warm, etc.’ Notice that we can eliminate options C through E because they do not use the required preposition TO after the verb ‘threaten’. Of the two options A and B, B is the better answer using the auxiliary verb ‘will’ as required to indicate a potential ‘future’ scenario ‘fifty years from now’.

Punch 4: Data Sufficiency

The roots of a quadratic equation ax^2+bx+c=0

are integers and a+b+c>0 and a>0. Are both the roots of the equation positive?

Sum of the roots is positive.

Product of the roots is positive.

Explanation:
Statement 1: Sum of the roots is positive.

i.e – b/a = p where p>0

i.e b = – (a x p).

Now consider the product of the roots.

Let c/a=q.

Clearly both p and q must be integers (since in the question it is given that both the roots are integers)

It is given that a+b+c>0

i.e a-(axp)+(axq)>0

i.e a(1-p+q)>0

It is given in the question that a>0

So (1-p+q)>0

i.e q-p>-1

i.e; q-p>=0 (since p and q are integers)

i.e q>=p

In statement 1 it is given that p>0. So clearly q>0

So from the first statement itself if sum is +ve we can conclude that product is also +ve.

Clearly Statement 2 alone is not sufficient.

So the answer is A

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mehovering said – Fri, 28 Nov 2008 01:08:42 -0000 ( Flag Edit Link )

I tried to look at your explanation but after couple of steps I just gave up. I am not sure till how far my logic to solve this question is correct but I prefer to give a logical and simple approach to a question, so here is what I feel:

STATEMENT 1: Sum of the roots is positive.

This can be possible even if the roots are 3 & -2 (3+ -2 = 1) and also if roots are 3 and 2. So in both the cases sum is positive but we don’t get any clear cut idea from statement 1 alone.

STATEMENT 2: Product of the roots is positive.

This too can be possible even if the roots are -3 & -2 and also if the roots are 3 and 2. So statement 2 alone is also not giving us a clear cut answer.

But if you will use both together then you can find that only 3 and 2 satisfies both the statement so using both the statement we can get the answer. HENCE IT IS “C”

I am not sure whether I am correct or not but the only thing I would like to stress on is that we should apply as simple as possible approach to a question as then only we can get a correct answer in a given time limit with a decent accuracy.

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mehovering said – Fri, 28 Nov 2008 00:51:38 -0000 ( Flag Edit Link )

It is B and C.
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Sureshbala said – Fri, 28 Nov 2008 05:10:48 -0000 ( Flag Edit Link )

Dear mehovring,

I think you are too fast in judging the abilities of Learnhub’s Team.

The answers are B and A without any doubt.

Coming to your data sufficiency explanation…..

You said the roots are 3 and -2.

Fine if the roots are 3 and -2, will a+b+c>0 ?

Absolutely No.

If the roots are 3 and -2, the quadratic equation is and it is clear that a+b+c here is equal to -6 which is not greater than 0, thus violating the condition a+b+c>0 in the question.

I think you should be a bit careful when you are dealing with data sufficiency of GMAT and more careful when you are trying to dismiss the solutions given by Learnhub team.

Also please read the rules before you participate here…..
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1. mehovering said – Fri, 28 Nov 2008 18:02:01 -0000 ( Flag Edit Link )
  
  Thanks a lot for your prompt reply!! Sure, I will follow the rules :)
  
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Blues said – Fri, 28 Nov 2008 14:28:39 -0000 ( Flag Edit Link )

Hi suresh bala can u explain more about roots, i think iam missing somewhere what i remebers is 2 roots is -a+ root ( b square – 4ac) and so on…kindly guide and wheres is today’s PUNCH
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Sureshbala said – Fri, 28 Nov 2008 15:10:47 -0000 ( Flag Edit Link )

Dear Blues,

You can quickly revise all the formulae of Quadratic Equations by going through the lesson Quadratic Expressions and Equations

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