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Did at least 15 percent of the children in Springfield suffer adverse
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19 Sep 2016, 04:47

2

7

00:00

A

B

C

D

E

Difficulty:

55% (hard)

Question Stats:

58% (01:29) correct 42% (01:37) wrong based on 161 sessions

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Did at least 15 percent of the children in Springfield suffer adverse effects after taking a certain vaccination?

(1) Among the Springfield children, 20 percent of the girls and more than 10 percent of the boys suffered adverse effects after taking the vaccination.

(2) Among the Springfield children, 20 percent of the boys and more than 15 percent of the girls suffered adverse effects after taking that vaccination.

Re: Did at least 15 percent of the children in Springfield suffer adverse
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19 Sep 2016, 07:02

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3

Bunuel wrote:

Did at least 15 percent of the children in Springfield suffer adverse effects after taking a certain vaccination?

(1) Among the Springfield children, 20 percent of the girls and more than 10 percent of the boys suffered adverse effects after taking the vaccination.

(2) Among the Springfield children, 20 percent of the boys and more than 15 percent of the girls suffered adverse effects after taking that vaccination.

Target question:Did at least 15 percent of the children in Springfield suffer adverse effects after taking a certain vaccination?

Statement 1: Among the Springfield children, 20% of the girls and more than 10% of the boys suffered adverse effects after taking the vaccination. This question tests an important (and often-tested) GMAT concept - weighted averages.

Let's say that 12% of the boys suffered adverse effects. There are three possible scenarios to consider: a) IF there were an EQUAL number of boys and girls, then the percentage of all children who suffered adverse effects would equal the average of 12% of 20%. So, the percentage of all children who suffered adverse effects would equal (20% + 12% )/2 = 16% b) IF there were an MORE girls than boys, then the percentage of all children who suffered adverse effects would be closer to 20% than to 12% c) IF there were an MORE boys than girls, then the percentage of all children who suffered adverse effects would be closer to 12% than to 20%

Now consider the following CONFLICTING cases Case a: 20% of the girls suffered adverse effects, and 20% of the boys suffered adverse effects. If there are 2 girls and 2 boys, then 20% of all children suffered adverse effects. Case b: 20% of the girls suffered adverse effects, and 11% of the boys suffered adverse effects. If there are 2 girls and 1000 boys, then the percentage of all children who suffered adverse effects will be very very close to 11%, since the boys have the bigger influence on the total percentage Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: Among the Springfield children, 20 percent of the boys and more than 15 percent of the girls suffered adverse effects after taking that vaccination. Since both groups (boys and girls) are such that EACH suffered more than 15% , then the COMBINED population is certain to have an adverse rate that's greater than 15% Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Did at least 15 percent of the children in Springfield suffer adverse
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19 Sep 2016, 06:05

Bunuel wrote:

Did at least 15 percent of the children in Springfield suffer adverse effects after taking a certain vaccination?

(1) Among the Springfield children, 20 percent of the girls and more than 10 percent of the boys suffered adverse effects after taking the vaccination.

(2) Among the Springfield children, 20 percent of the boys and more than 15 percent of the girls suffered adverse effects after taking that vaccination.

Stat 1: let x be for boys and y be girls

0.2(y)+ >0.1(x)...we can't say anything from this.

Stat 2: 0.2(x) + > 0.15(y)... since we have information here itself that more than 15 percent of the girls suffered adverse effects... we can say that > 15% of children suffer adverse effects when we club boys information too...I go for B.

Re: Did at least 15 percent of the children in Springfield suffer adverse
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04 Dec 2017, 10:04

Bunuel wrote:

Did at least 15 percent of the children in Springfield suffer adverse effects after taking a certain vaccination?

(1) Among the Springfield children, 20 percent of the girls and more than 10 percent of the boys suffered adverse effects after taking the vaccination.

(2) Among the Springfield children, 20 percent of the boys and more than 15 percent of the girls suffered adverse effects after taking that vaccination.

If the total number of people is made up of X and Y (Thus total being X+Y), and we are given an attribute that is shared by a% of these X people, and b% of these y people, and we are asked what is the overall % of people (out of total X+Y) who share this attribute, then that % will always be between a and b. So overall % in these cases will be somewhere between the two. Now if value of X is more than Y, answer will be closer to a, and vice-versa. This is a concept of weighted average and can be applied in this question.

(1) We dont know how many girls are there and how many boys are there. But since this effect is present in 20% of girls and more than 10% of boys, overall percent children with this effect would lie somewhere between 10% and 20%. If the number of girls is more than boys, children affected would be more than 15%, but if number of boys is more, it could be less than 15% (we dont even know whats the exact percentage of boys affected). So Insufficient.

(2) 20% of boys affected, more than 15% of girls affected. By same concept, overall children affected would be somewhere between 20% and 15%, thus more than 15% definitely. Sufficient.

Hence B answer

gmatclubot

Re: Did at least 15 percent of the children in Springfield suffer adverse &nbs
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04 Dec 2017, 10:04