In a survey of 150 persons, how many were smokers and drinkers?
(1) 80 percent of the person surveyed were drinkers.
(2) 40 percent of the smokers were drinkers also.
[spoiler]Source: Crack-GMAT
www.crack-GMAT.com[/spoiler]
smokers and drinkers
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IMO Csanju09 wrote:In a survey of 150 persons, how many were smokers and drinkers?
(1) 80 percent of the person surveyed were drinkers.
(2) 40 percent of the smokers were drinkers also.
[spoiler]Source: Crack-GMAT
www.crack-GMAT.com[/spoiler]
make a box with smokers and drinkers,non smokers and non drinkers
stmnt 1: 120 people were drinkers no other info insuff
stmnt 2:doesnt help u either.
combining 120 were drinkers and 40% of it will give u the answer
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how could 40 percent of drinkers answer the stem, can you please show your cards?aloneontheedge wrote:IMO Csanju09 wrote:In a survey of 150 persons, how many were smokers and drinkers?
(1) 80 percent of the person surveyed were drinkers.
(2) 40 percent of the smokers were drinkers also.
[spoiler]Source: Crack-GMAT
www.crack-GMAT.com[/spoiler]
make a box with smokers and drinkers,non smokers and non drinkers
stmnt 1: 120 people were drinkers no other info insuff
stmnt 2:doesnt help u either.
combining 120 were drinkers and 40% of it will give u the answer
The mind is everything. What you think you become. -Lord Buddha
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Quantitative Instructor
The Princeton Review - Manya Abroad
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drinkers nondrinkers totalsanju09 wrote:how could 40 percent of drinkers answer the stem, can you please show your cards?aloneontheedge wrote:IMO Csanju09 wrote:In a survey of 150 persons, how many were smokers and drinkers?
(1) 80 percent of the person surveyed were drinkers.
(2) 40 percent of the smokers were drinkers also.
[spoiler]Source: Crack-GMAT
www.crack-GMAT.com[/spoiler]
make a box with smokers and drinkers,non smokers and non drinkers
stmnt 1: 120 people were drinkers no other info insuff
stmnt 2:doesnt help u either.
combining 120 were drinkers and 40% of it will give u the answer
smokers X
non smokers
120(stem1) 30=(150-120) 150
clearly stmtn 1 is not suff
stmnt 2 is not suff either
combining 40 percent of the smokers were drinkers also(marked as X) which is 0.4*120=48
hope this is clear.i do not know how to draw.If you tried attempting this using venn diagram,it wud have been complicated
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Venn diagram is the only time saving and safer way to solve this problem, which we are not really supposed to on DS though, but as a matter of fact, the idea to arrive at a decision A through E whatever, must not be deceptive, otherwise the choice could be wrong in most of the cases, as in this case.aloneontheedge wrote:drinkers nondrinkers totalsanju09 wrote:how could 40 percent of drinkers answer the stem, can you please show your cards?aloneontheedge wrote:IMO Csanju09 wrote:In a survey of 150 persons, how many were smokers and drinkers?
(1) 80 percent of the person surveyed were drinkers.
(2) 40 percent of the smokers were drinkers also.
[spoiler]Source: Crack-GMAT
www.crack-GMAT.com[/spoiler]
make a box with smokers and drinkers,non smokers and non drinkers
stmnt 1: 120 people were drinkers no other info insuff
stmnt 2:doesnt help u either.
combining 120 were drinkers and 40% of it will give u the answer
smokers X
non smokers
120(stem1) 30=(150-120) 150
clearly stmtn 1 is not suff
stmnt 2 is not suff either
combining 40 percent of the smokers were drinkers also(marked as X) which is 0.4*120=48
hope this is clear.i do not know how to draw.If you tried attempting this using venn diagram,it wud have been complicated
In Set language
n (D) = 120, and n (D & S) = 0.40 X n (S) is the golden question here. Although, we have
n (D & S) = n (D) + n (S) - n (D or S) = 120 + n (S) - 150
or n (D & S) = n (S) - 30, can we figure out n (S)?
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
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www.manyagroup.com
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that is wat i have done it but in a box which avoids much of calculation. Its all abt perception.i feel box method works much quicker for mesanju09 wrote:Venn diagram is the only time saving and safer way to solve this problem, which we are not really supposed to on DS though, but as a matter of fact, the idea to arrive at a decision A through E whatever, must not be deceptive, otherwise the choice could be wrong in most of the cases, as in this case.aloneontheedge wrote:drinkers nondrinkers totalsanju09 wrote:how could 40 percent of drinkers answer the stem, can you please show your cards?aloneontheedge wrote:IMO Csanju09 wrote:In a survey of 150 persons, how many were smokers and drinkers?
(1) 80 percent of the person surveyed were drinkers.
(2) 40 percent of the smokers were drinkers also.
[spoiler]Source: Crack-GMAT
www.crack-GMAT.com[/spoiler]
make a box with smokers and drinkers,non smokers and non drinkers
stmnt 1: 120 people were drinkers no other info insuff
stmnt 2:doesnt help u either.
combining 120 were drinkers and 40% of it will give u the answer
smokers X
non smokers
120(stem1) 30=(150-120) 150
clearly stmtn 1 is not suff
stmnt 2 is not suff either
combining 40 percent of the smokers were drinkers also(marked as X) which is 0.4*120=48
hope this is clear.i do not know how to draw.If you tried attempting this using venn diagram,it wud have been complicated
In Set language
n (D) = 120, and n (D & S) = 0.40 X n (S) is the golden question here. Although, we have
n (D & S) = n (D) + n (S) - n (D or S) = 120 + n (S) - 150
or n (D & S) = n (S) - 30, can we figure out n (S)?
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But how can we answer the stem without knowing n (S) here? I personally agree with C, but your assumption that 40 percent of n (D) will give us the answer seems fishyaloneontheedge wrote: that is wat i have done it but in a box which avoids much of calculation. Its all abt perception.i feel box method works much quicker for me
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
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www.manyagroup.com
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We want the number of people who belong to both groups, smokers and drinkers.sanju09 wrote:In a survey of 150 persons, how many were smokers and drinkers?
(1) 80 percent of the person surveyed were drinkers.
(2) 40 percent of the smokers were drinkers also.
[spoiler]Source: Crack-GMAT
www.crack-GMAT.com[/spoiler]
(1) gives us the number of drinkers, but nothing about smokers: insufficient, eliminate A and D.
(2) doesn't give us any actual numbers: insufficient, eliminate B.
Together: we know that 40% of the smokers are also drinkers, but we don't know what percent of the drinkers are smokers; since we only have information about the number of drinkers, we still can't answer the question: choose E.
We could also pick numbers to show that we can get multiple answers.
From (1), we know that we have 120 drinkers.
From (2), we know that 40% of the smokers are drinkers. We could have:
10 smokers, 4 of whom are drinkers, so the answer would be "4"; or
20 smokers, 8 of whom are drinkers, so the answer would be "8".
Since we can generate multiple answers, we can't answer the question - even together, insufficient.
(We can't make any assumptions in DS - nowhere does it say that all 150 had to be smokers or drinkers or both.)
![Image](https://i.imgur.com/YCxbQ7s.png)
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Let me quote myself to continue from there, please
Since, n (D & S) = 0.40 X n (S), therefore
n (S) - 30 = 0.40 X n (S), [spoiler]hence C, only if 150 are either smokers or drinkers.[/spoiler].
Yes, we can figure out n (S), see howIn Set language
n (D) = 120, and n (D & S) = 0.40 X n (S) is the golden question here. Although, we have
n (D & S) = n (D) + n (S) - n (D or S) = 120 + n (S) - 150
or n (D & S) = n (S) - 30, can we figure out n (S)?
Since, n (D & S) = 0.40 X n (S), therefore
n (S) - 30 = 0.40 X n (S), [spoiler]hence C, only if 150 are either smokers or drinkers.[/spoiler].
The mind is everything. What you think you become. -Lord Buddha
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www.manyagroup.com
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No, E is really the correct answer to the question.sanju09 wrote:Let me quote myself to continue from there, please
Yes, we can figure out n (S), see howIn Set language
n (D) = 120, and n (D & S) = 0.40 X n (S) is the golden question here. Although, we have
n (D & S) = n (D) + n (S) - n (D or S) = 120 + n (S) - 150
or n (D & S) = n (S) - 30, can we figure out n (S)?
Since, n (D & S) = 0.40 X n (S), therefore
n (S) - 30 = 0.40 X n (S), [spoiler]hence C[/spoiler].
Please explain why the two possible answers I provide can't both be true based on the information given.
Remember, it's possible that some people are neither smokers nor drinkers.
![Image](https://i.imgur.com/YCxbQ7s.png)
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Please read under spoiler too, it reads E, otherwise
The mind is everything. What you think you become. -Lord Buddha
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I don't see that anywhere in the post, but I'll take your word for it!sanju09 wrote:Please read under spoiler too, it reads E, otherwise
![Image](https://i.imgur.com/YCxbQ7s.png)
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Under the spoiler was written: [spoiler]C, only if 150 are either smokers or drinkers; otherwise E is always true[/spoiler]
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
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www.manyagroup.com
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Since total number of drinkers are 120(i made a mistake while taking a screen shot,it reads as smokers)sanju09 wrote:Under the spoiler was written: [spoiler]C, only if 150 are either smokers or drinkers; otherwise E is always true[/spoiler]
x +y = 120
x = 0.4*120
hence C
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The point raised by Stuart Kovinsky, that we can't make any assumptions in DS - nowhere does it say that all 150 had to be smokers or drinkers or both; is sufficient to accept [spoiler]E[/spoiler] as the right answer here.aloneontheedge wrote:Since total number of drinkers are 120(i made a mistake while taking a screen shot,it reads as smokers)sanju09 wrote:Under the spoiler was written: [spoiler]C, only if 150 are either smokers or drinkers; otherwise E is always true[/spoiler]
x +y = 120
x = 0.4*120
hence C
[spoiler]Let's thank him from the deepest part of our hearts now[/spoiler]
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
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Sanjeev K Saxena
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