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In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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24 Apr 2013, 10:01

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In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Which of the following must be true on the basis of the statements above?

(A) There were fewer cases of schistosomiasis last year than five years ago.

(B) The percentage of disease cases from malaria has increased over the past 5 years.

(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%.

(D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis.

(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%.

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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24 Apr 2013, 10:45

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its E : think like this : if initially the total number of disease were 100 then S accounted for 40 case now if increase these cases of S even to 41 then total number of cases of disease must be made to around 136 ----> which means that total number of diseases have increased by more than 30 percent !!

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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24 Apr 2013, 14:34

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In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Which of the following must be true on the basis of the statements above?

A) There were fewer cases of schistosomiasis last year than five years ago. Wrong. The fact that the percentage is less than that in the past does not mean the absolute value is also less. ==> Eliminate right away.

B) The percentage of disease cases from malaria has increased over the past 5 years. Wrong. No information of percentage of disease cases from malaria in the past ==> Eliminate right away.

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%. Wrong. Quite confused. However, it's wrong because of "some disease" is not clear. In this question, we just talk about Malaria and schistosomiasis.

D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. Wrong. Shell game. But it's wrong because it says "Each year".

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%. Correct. five years ago, the number of schistosomiasis cases was 40/100 total number of disease cases (40%). Last year, the number of schistosomiasis was 60 ==> Total number of disease cases was (60 /30%)x100% = 200 ==> Total disease cases increased 100% that is more than 30%.
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If the percentage of cases has dropped from 40 to 30, that means there are 3/4 as many cases per 100 as there were before. In order for the actual number to go up, there needs to be an increase in the total disease cases of more than 4/3. (3/4 x 4/3 = 1, so anything greater than 4/3 will lead to an increase.) This means that for the # of cases of schistosomiasis to go up, we need an increase of more than 1/3. E is correct.

C, on the other hand, is saying something that *seems* kind of sensible. If the % of schistosomiasis cases goes down, and the total number doesn't drop drastically, then doesn't something else need to go down? The answer is no. If schistosomiasis goes down, and everything else stays the same, it can represent 30% of all cases without anything else having to go up. This leads to a drop in total cases of about 15%.

To illustrate, imagine that the original breakdown is like this: 51 cases of malaria, 40 cases of schistosomiasis, and 9 cases of flu. What # of schistosomiasis cases would yield a new % of 30 if the # of malaria and flu cases stay the same? Schist/Total = s/(51+9+s) = .30 s = .3(60 + s) .7s = 18 s is about 25, so the new total is about 85, which is just a 15% drop.

Don't you love doing algebra in the verbal section? :/
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Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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03 May 2013, 00:44

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In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Which of the following must be true on the basis of the statements above?

A. There were fewer cases of schistosomiasis last year than five years ago.

B. The percentage of disease cases from malaria has increased over the past 5 years.

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%.

D. Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis.

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%.
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Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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03 May 2013, 05:01

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I think this one is harder than 600-700. Don't you?

thelosthippie wrote:

In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Schistosomiasis, malaria: main diseases.

Quote:

Which of the following must be true on the basis of the statements above?

A. There were fewer cases of schistosomiasis last year than five years ago.

Percentages are not equivalent to absolute number. Misleading.

Quote:

B. The percentage of disease cases from malaria has increased over the past 5 years.

Not really. The percentage given for malaria is the arithmetic average for the last 5 years. I.e. the percentages for each year could be manipulated greatly without changing the mean.

Quote:

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%.

Can be true, but doesn't have to. This 30% is really confusing here, but it's a red herring. Don't let it possess your mind.

Quote:

D. Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis.

False for the same reason as B.

Quote:

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%.

Percentage value decreased. If the total number increased concurrently, then the total number of diseases had to increase even more. Count the given 30% if you have time on the GMAT, it's not necessary after all. Correct.
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Last edited by HumptyDumpty on 01 Aug 2014, 07:27, edited 1 time in total.

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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03 May 2013, 05:22

E is correct..

A. There were fewer cases of schistosomiasis last year than five years ago...% and no. (quantity) should not be compared..wrong

B. The percentage of disease cases from malaria has increased over the past 5 years....cant say..we only know that the avg. of past five years....wrong

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%. ...well..close one..but it says SOME DISEASE..but we want to know relation with all other disease cases..wrong..

D. Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis.,.cant say...same as B

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%....correct...if all other cases have increase then they have to increase by more than 30% because schistosomiasis cases have reduced form 40% to 30%.. _________________

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Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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03 Jul 2014, 06:29

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Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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05 Jul 2014, 03:55

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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13 Jul 2014, 01:00

manugmat123 wrote:

In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Which of the following must be true on the basis of the statements above?

A) There were fewer cases of schistosomiasis last year than five years ago. B) The percentage of disease cases from malaria has increased over the past 5 years. 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%. D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. 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%.

As soon as we see %, there will be some catch with total number of cases. A) There were fewer cases of schistosomiasis last year than five years ago - Cannot be inferred B) The percentage of disease cases from malaria has increased over the past 5 years - Cannot be inferred 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%. This is not possible as "S" % wise went down, so if the total number of cases of "S" went up, the total number of all cases has to go up and not down

D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis We don't have each year data, cannot be infered 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%. Looks ok. Calculation wise. 5 years back for "S" disease 100 Total cases - "S" disease - 40 - Percentage = 40% if we have to maintain the same cases Percentage = 30% "S" disease cases = 40 Then total should be close to 130 as 13*3 = 39 Hence Option E) _________________

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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17 Jul 2015, 04:37

DmitryFarber wrote:

How about a fraction approach?

If the percentage of cases has dropped from 40 to 30, that means there are 3/4 as many cases per 100 as there were before. In order for the actual number to go up, there needs to be an increase in the total disease cases of more than 4/3. (3/4 x 4/3 = 1, so anything greater than 4/3 will lead to an increase.) This means that for the # of cases of schistosomiasis to go up, we need an increase of more than 1/3. E is correct.

C, on the other hand, is saying something that *seems* kind of sensible. If the % of schistosomiasis cases goes down, and the total number doesn't drop drastically, then doesn't something else need to go down? The answer is no. If schistosomiasis goes down, and everything else stays the same, it can represent 30% of all cases without anything else having to go up. This leads to a drop in total cases of about 15%.

To illustrate, imagine that the original breakdown is like this: 51 cases of malaria, 40 cases of schistosomiasis, and 9 cases of flu. What # of schistosomiasis cases would yield a new % of 30 if the # of malaria and flu cases stay the same? Schist/Total = s/(51+9+s) = .30 s = .3(60 + s) .7s = 18 s is about 25, so the new total is about 85, which is just a 15% drop.

Don't you love doing algebra in the verbal section? :/

Hello Dmitry, Could you please explain I could get this part If the percentage of cases has dropped from 40 to 30, that means there are 3/4 as many cases per 100 as there were before But after 4/3 is of what (number of total number of cases before or now ) ? Thanks

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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17 Jul 2015, 04:38

DmitryFarber wrote:

How about a fraction approach?

If the percentage of cases has dropped from 40 to 30, that means there are 3/4 as many cases per 100 as there were before. In order for the actual number to go up, there needs to be an increase in the total disease cases of more than 4/3. (3/4 x 4/3 = 1, so anything greater than 4/3 will lead to an increase.) This means that for the # of cases of schistosomiasis to go up, we need an increase of more than 1/3. E is correct.

C, on the other hand, is saying something that *seems* kind of sensible. If the % of schistosomiasis cases goes down, and the total number doesn't drop drastically, then doesn't something else need to go down? The answer is no. If schistosomiasis goes down, and everything else stays the same, it can represent 30% of all cases without anything else having to go up. This leads to a drop in total cases of about 15%.

To illustrate, imagine that the original breakdown is like this: 51 cases of malaria, 40 cases of schistosomiasis, and 9 cases of flu. What # of schistosomiasis cases would yield a new % of 30 if the # of malaria and flu cases stay the same? Schist/Total = s/(51+9+s) = .30 s = .3(60 + s) .7s = 18 s is about 25, so the new total is about 85, which is just a 15% drop.

Don't you love doing algebra in the verbal section? :/

Hello Dmitry, Could you please explain I could get this part If the percentage of cases has dropped from 40 to 30, that means there are 3/4 as many cases per 100 as there were before But after 4/3 is of what (number of total number of cases before or now ) ? Thanks

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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08 Aug 2015, 06:00

I got this question correct. Eliminated A B D. B/w C and E, without algebra I got the hint that what E is trying to say.

C talks about other disease. so eliminated.

I would still like to know what option C says. I could not comprehend this option in exam. Even now I am not able to understand whats its trying to say. I could still not understand from above answer what C means.

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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14 Aug 2015, 07:53

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manugmat123 wrote:

In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year.

Which of the following must be true on the basis of the statements above?

A) There were fewer cases of schistosomiasis last year than five years ago. B) The percentage of disease cases from malaria has increased over the past 5 years. 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%. D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. 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%.

E basically says-(if..hypothetical.....)

If 40% x < 30 % y , (where x = total cases 5 years ago and y= total cases in past year)

then ( y-x )/x > 1/3 ( after solving the inequality stated )

hence , increase IN TOTAL number of cases has been more than 33.3 % ( 33.33% is more than 30 %)

The above can be true based on the argument.

Hope the simple inequality helps state why E is right.

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Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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06 Jan 2016, 04:44

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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01 Feb 2016, 10:02

Quote:

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%.

Let X= total number of diseases before 5 years: A=Number of malaria victims before 5 years=40/100 X

Y=total number of diseases now : B=Number of malaria victims now=30/100 Y

Assume worst case A=B that is 40/100*X=30/100*Y Then Y= 40/30*X= 1*1/3*X which means that Y is 133.33 % of X.Which means present population is more than 30% of population 5 years ago.

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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23 Aug 2016, 07:19

I have a small doubt in this question and i request people to clarify ,

I chose option D and was wrong . It is mentioned in the premise that " Over the past five years, malaria has accounted for more than half of all disease cases " , so i inferred that every year malaria has accounted for more than 50% of the cases . cant we conclude that " Over the past 5 years " means all the years within the range of those 5 years ?

because if we can conclude that Malaria did account for more than 50% for all 5 years , then schistosomiasis would naturally account for less than 50% over these years and then we can easily conclude that option D would be correct

Re: In a certain population, the two most heavily diagnosed diseases are s [#permalink]

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23 Aug 2016, 09:32

rohitmilind007ster wrote:

I have a small doubt in this question and i request people to clarify ,

I chose option D and was wrong . It is mentioned in the premise that " Over the past five years, malaria has accounted for more than half of all disease cases " , so i inferred that every year malaria has accounted for more than 50% of the cases . cant we conclude that " Over the past 5 years " means all the years within the range of those 5 years ?

because if we can conclude that Malaria did account for more than 50% for all 5 years , then schistosomiasis would naturally account for less than 50% over these years and then we can easily conclude that option D would be correct

It says "over the past five years,...cases" --> average is more than 50 % not each year. One year it can be 99% and other year it can be less than 30%. The number varies but average is more than 50%. I also fell in to this trap.

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