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26 Jan 2021, 06:49
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26 Jan 2021, 10:06
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warrior1991
Hello, warrior1991. This is a case in which the process of elimination makes more sense than simply knowing what must be correct. How about we jump into the answers with an eye on disproving what cannot be supported by the passage?
manugmat123
You should know from Quant that percents do not necessarily translate to the actual number of something. Here, 30 percent from year two could be greater than 40 percent from year one if the certain population had grown from one year to the other. This should be an easy elimination.
manugmat123
Just because the percentage of disease cases from schistosomiasis has decreased, we cannot say that that from malaria has necessarily increased. That could be true, but it could also be true that the percentage of disease cases from malaria has remained the same or even decreased while the percent of disease cases from other diseases has increased. We simply do not have enough information to tell one way or another.
manugmat123
The latter part of this is confusing to me, so rather than sort out what, exactly, it was saying, I just placed it on hold and moved on. If I can find an easier target or, with luck, get behind an answer choice, I would much rather work from a place of comfort. What gives me pause here is the vague some, as well as this emphasis on the number of cases. More on that below.
manugmat123
We do not have information about annual comparisons, only about the present versus five years ago. Whew, this is just the sort of easy target we should be looking to knock down.
manugmat123
I like the hypothetical (conditional) framework here, unlike the definitive language used in (C). Also, we can focus on schistosomiasis rather than some disease from before. I like the way DmitryFarber has gone about proving this one, but consider the pertinent facts about schistosomiasis given in the passage:
1) percentage of disease cases five years ago: 40
2) percentage of disease cases last year: 30
To keep matters simple, imagine an initial population of 100 who have been diagnosed with disease. This means that 40 people from this initial population were diagnosed with schistosomiasis. Now, five years later, if 30 percent of the population represents more than 40 people, we can deduce the following (in which P represents this total population):
\(0.30P > 40\)
\(P > \frac{40}{0.3}\)
\(P > \frac{400}{3}\)
\(P > 133.33\)
If the population of those diagnosed with disease has increased from 100 to at least 133, then (E) must be true, and we do not have to go back and fuss about (C). Case closed.
If an answer choice looks as if it will be a time sink, then I will sometimes skip it, call it a yellow light answer, and move on, always looking to work from a place of comfort. In this case, I was still able to arrive at the correct conclusion within two minutes, and by not worrying about (C), I would be setting myself up mentally for the next question. (Had (E) not worked out, I would have chosen (C), again without having gone back to it. If I have disproved the other answers, then I will feel confident choosing the odd one out, but that, I suppose, comes with practice, and not everyone would agree with such a method.)
I hope that helps. Thank you for thinking to ask me.
- Andrew
27 Jan 2021, 00:48
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manugmat123
Over 5 years, malaria is more than 50%. (So add all malaria cases of 5 years and all disease cases for 5 years, and malaria cases account for more than 50%. It does not say that each year more than 50% were malaria cases. It just says over the last 5 years.)
5 yrs ago, S cases accounted for more than 40%.
Last year, S cases accounted for 30%.
(We don't know what happened in between.)
Note that we are given malaria and S cases as percentage of total disease cases. The actual numbers are unknown. They will depend on how many disease cases were diagnosed each year. It is something like market share. You can imagine a pie chart to help you see clearly.
(A) There were fewer cases of schistosomiasis last year than five years ago.
Not necessary.
5 yrs ago: 100 total cases. 40 cases of S.
Last year: 200 total cases. 60 cases of S.
(B) The percentage of disease cases from malaria has increased over the past 5 years.
No. We don't know the percentage of the period before the past 5 years. We just that it has been more than 50% over the last 5 years period.
(C) Some disease has experienced an increase in the number of its total cases, as long as the total number of disease cases went down by a number less than 30%.
Not necessary. I don't need to take numbers here. What if there were some new diseases last year? Then this statement can easily be false. There NEEDS to be no disease whose numbers have increased. I don't even need to evaluate it.
(D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis.
We don't know what happened year on year in case of malaria and neither in case of S.
(E) If the total number of schistosomiasis cases increased over the past five years, then the total number of disease cases must have increased by more than 30%.
We need number of S cases to increase. Let's see whether more than 30% is needed to increase the S cases.
5 yrs ago: 100 total cases. 40 cases of S.
Last year: Say 40 cases of S.
The 40 will be 30% of total cases last year.
40 = 30% of C
C = 133.33
So to maintain the same number of cases of S, the number of total disease cases must increase by 33.33%. Then to increase the number of cases of S, the total number of disease must certainly increase by more than 33.33%.
This statement is true.
Answer (E)
