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# Epidemiologist: In Brazil, schistosomiasis and malaria are

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Re: Epidemiologist: In Brazil, schistosomiasis and malaria are  [#permalink]

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14 Jan 2018, 04:21
Very tough..IMO OA is A
In my case, I was confused between A and E
This is my reasoning

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
-> Keep
B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.
-> 'treatment regimens' : Out of scope
C. Five years ago, many more people died from schistosomiasis than died from malaria.
-> incorrect.
Let's suppose malaria is more fatal than schistomiasis. Then we do not need to think about the percentage.
D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
-> Incorrect. This is just a fact.
E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.
-> Keep

I chose A, because let's suppose there is another disease C.
If the percentage of C is 90%, then E can weaken the passage.
But in A, for example, the percentage of schistosomiasis was always 50%, but the percentage of malaria was changed suddenly
,for example, 5% to 50%(Because schistosomiasis was always 50%), it can strengthen the passage.
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Re: Epidemiologist: In Brazil, schistosomiasis and malaria are  [#permalink]

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15 Jan 2018, 03:55
HG0815 wrote:
Very tough..IMO OA is A
In my case, I was confused between A and E
This is my reasoning

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
-> Keep
B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.
-> 'treatment regimens' : Out of scope
C. Five years ago, many more people died from schistosomiasis than died from malaria.
-> incorrect.
Let's suppose malaria is more fatal than schistomiasis. Then we do not need to think about the percentage.
D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
-> Incorrect. This is just a fact.
E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.
-> Keep

I chose A, because let's suppose there is another disease C.
If the percentage of C is 90%, then E can weaken the passage.
But in A, for example, the percentage of schistosomiasis was always 50%, but the percentage of malaria was changed suddenly
,for example, 5% to 50%(Because schistosomiasis was always 50%), it can strengthen the passage.

C cannot be 90% since two most common infectious diseases are malaria and schistosomiasis.

(E) is irrelevant since we are comparing malaria vs schistosomiasis increase. What happened to the number of others is immaterial.

We see that number of schistosomiasis cases has increased substantially. If the percentage of infectious disease cases caused by schistosomiasis has remained same, but the percentage of cases caused by malaria has increased substantially but still in actual number terms, the number of cases of schistosomiasis is the same, it could mean that the initial percentage of schistosomiasis cases was more.

Say if x% cases were of schistosomiasis 5 yrs ago and y% of malaria, assuming that the percentage of cases of schistosomiasis remains constant, when will they account for most of the new disease cases? The number of new cases of schistosomiasis will be x% of the additional number of total cases. They will be majority of the new cases if x > 50%.
Hence (A) works.
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Re: Epidemiologist: In Brazil, schistosomiasis and malaria are  [#permalink]

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16 Jan 2018, 01:42
srishti201996 wrote:
mikemcgarry GMATNinja VeritasPrepKarishma

Can you please shed more light on D?

Karishma you gave the following explanation :

D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
This says that % of malaria cases was not much greater (though perhaps a little greater) than % of schistosomiasis cases over the past 5 years. If anything, this weakens our conclusion. It indirectly implies that out of 100 cases 5 yrs ago, malaria cases were slightly more than schistosomiasis cases.

Can you please tell me if my understanding of this is correct?
Say there were 100 cases 5 years ago!
51%-M - 51 cases
49%-S- 49 cases

so S cases were less than M but since now S is the cause of most cases, S would have increased over time.

But we can't say S was greater 5 years ago?

Am i right?

If schistosomiasis has been primarily responsible for the overall increase in infectious disease cases over the past 5 years and we want to conclude that there must have been more cases of schistosomiasis 5 years ago, we need to say that percentage of schistosomiasis cases has either remained same or decreased slightly.
Only then , if today too they are majority in number in the extra cases, they must have been majority in number 5 years back too.
So (A) works.

Let's look at (D).
Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
(D) says that percentage of malaria cases was not significantly greater than percentage of schistosomiasis cases. We actually want the percentage of schistosomiasis cases to be higher than those of malaria over the past 5 yrs so that majority of extra cases are of schistosomiasis. So option (D) does not work.
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Re: Epidemiologist: In Brazil, schistosomiasis and malaria are  [#permalink]

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16 Jan 2018, 17:38
srishti201996 wrote:
mikemcgarry GMATNinja VeritasPrepKarishma

Can you please shed more light on D?

Karishma you gave the following explanation :

D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
This says that % of malaria cases was not much greater (though perhaps a little greater) than % of schistosomiasis cases over the past 5 years. If anything, this weakens our conclusion. It indirectly implies that out of 100 cases 5 yrs ago, malaria cases were slightly more than schistosomiasis cases.

Can you please tell me if my understanding of this is correct?
Say there were 100 cases 5 years ago!
51%-M - 51 cases
49%-S- 49 cases

so S cases were less than M but since now S is the cause of most cases, S would have increased over time.

But we can't say S was greater 5 years ago?

Am i right?

Dear srishti201996,

I'm happy to respond.

My friend, context is everything. The prompt says, "Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases." That's evidence. That means that when we look at the total number of new cases of infectious disease, schistosomiasis accounts for well over 50% of them. If the number new cases of malaria were anything close, anything comparable, to the number of new cases of schistosomiasis, then this statement would be false. To say one thing is primarily responsible is to say that all other things combined are, in aggregate, not as powerful, not as influential, as that one thing. This is absolutely crucial to keep in mind with this argument.

Choice (D) directly contradicts this piece of evidence.
D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
If about the same number of people had one or the other, then it would be patently false to say that only schistosomiasis was "primarily responsible for the overall increase in infectious disease cases."
This directly contradicts the evidence in the prompt. That's not the sign of a good strengthener!

Does this make sense?
Mike
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Re: Epidemiologist: In Brazil, schistosomiasis and malaria are  [#permalink]

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19 Oct 2018, 18:48

Premise - Schist has been primarily responsible for the infectious disease.
Conclusion - the number of Schist case may be greater than the number of Mala case.

This is a typical % vs # question.

A is clearly not good enough. Although Schist % could remain unchanged, there is no promise that the change in Mala % won't go beyond the final Schist %. And please note, Schist and Mala are two "common" diseases but not the "only" diseases. So there are other infectious diseases. Let's say that 5 years ago, Schist had 40%, Mala had 35%, and other together had 25%. Option A can easily goes to a situation that after 5 years, Schist still has 40% but Mala has 45%, and the other together has 15%. In this situation, Option A won't strengthen the argument. And to make it strengthen, you will have to make additional (out of scope) assumption that Mala's % won't go beyond Schist's %.

The good answer is B. There is no answer here that is good enough to address the # so purely working on the % is the only way. B tells us that the data trend has been like this for so long, making the case that Schist was the major player 5 years ago very convincing. Imagine, if Schist was the major play and the trend barely changed, then of course we could be so sure that Schist was definitely primarily responsible.

Same logic - Bill Gates was the richest. If the richman ranking has been unchanged for so long. Of course Bill Gates had more money than the others, no doubt.
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Re: Epidemiologist: In Brazil, schistosomiasis and malaria are  [#permalink]

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21 Oct 2018, 02:28
thelosthippie wrote:
Epidemiologist: In Brazil, schistosomiasis and malaria are the two most common infectious diseases. Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases. Therefore it is likely that there were more cases of schistosomiasis than malaria five years ago.

Which of the following most strengthens the argument above?

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.

B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.

C. Five years ago, many more people died from schistosomiasis than died from malaria.

D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.

E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.

Epidemiologist: In Brazil, schistosomiasis and malaria are the two most common infectious diseases. Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases. Therefore it is likely that there were more cases of schistosomiasis than malaria five years ago.
Understand :
1) S and M are most common [ ie. if there are 100 cases of infec diseases , S and M account for more than 50 (S+M>50%)
2)S is the major contributor for the INCREASE for IDs

Conclusion: FIVE YEARS AGO - number of cases of S>M ( note : NUMBER OF CASES)

Prethinking :
let cases with scisht = S
Cases with malaria = M
other cases = O
Therefore : S+M+O =100

New cases =50
S= 30 (assumed as per given info as S is MAJOR contributor for INCREASE)
M= 15( assumed as per given info as S and M both are MOST COMMON so M will still be GREATER than OTHER cases
O=5

Conclusion : before the increase S>M

Do not try to prethink here as there will be 3 cases which you would have to test in order to concur with the conclusion

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
: Now as per given ans choice the percentage of cases 5 years ago and over past 5 years is the SAME and percentage of M has inreased (Note: percentage is given and not numbers)
5 years ago : no. of Schiest = S
suppose S account for (x) percent for all cases.--- S= (x)/100 * total cases (100) ........ (1)

over past 5 yrs : total number of sciest cases : S+30
As per A : S+30 = (x)/100 * new total cases (150)........ (2)

Therefore : substitute value of (x)/100 from (1) in (2)

S+30= S/100 *150
Solve for S >> S=60

Therefore , M has to be less than or equal to 40 but cannot be greater than 40..... Therfore the conclusion = S>M
Re: Epidemiologist: In Brazil, schistosomiasis and malaria are &nbs [#permalink] 21 Oct 2018, 02:28

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