At a certain picnic, each of the guests was served either a : GMAT Data Sufficiency (DS)
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# At a certain picnic, each of the guests was served either a

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15 Oct 2012, 03:41
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At a certain picnic, each of the guests was served either a single scoop or a double scoop of ice cream. How many of the guests were served a double scoop of ice cream?

(1) At the picnic, 60 percent of the guests were served a double scoop of ice cream.
(2) A total of 120 scoops of ice cream were served to all the guests at the picnic.

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[Reveal] Spoiler: OA

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15 Oct 2012, 03:41
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At a certain picnic, each of the guests was served either a single scoop or a double scoop ice-cream. How many of the guests were served a double scoop of ice-cream?

(1) At the picnic, 60 percent of the guests were served a double scoop of ice-cream --> $$\frac{x}{y}=\frac{4}{6}=\frac{2}{3}$$, where $$x$$ is the # of people served single scoop and $$y$$ the # of people served double scoop. Clearly insufficient to calculate single numerical value of $$y$$.

(2) A total of 120 scoops of ice-cream were served to all the guests at the picnic --> $$1*x+2*y=120$$. Again not sufficient.

(1)+(2) $$x=\frac{2}{3}y$$ and $$x+2y=120$$: we have 2 distinct linear equations with 2 unknowns, hence we can solve for $$x$$ and $$y$$. Sufficient. (Just to illustrate: $$\frac{2}{3}y+2y=120$$ --> $$y=45$$)

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15 Oct 2012, 04:12
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Let the total number of guests be 100x
1) 60x , where x can be anything --->Insufficient
2) Clearly insufficient
1+2) No of guests who are served single scoop = 40x
No of guests who are served double scoop = 60x
Total no of scoops served - 40x (1) + 60x(2) = 160x
Total no of scoops served is 120
Thus 120 = 160x
We can get Unique value of 60x which will 60x (120/160) = 45 --->Sufficient

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Re: At a certain picnic, each of the guests was served either a [#permalink]

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15 Oct 2012, 07:57
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1) Only a percentage is given. Nothing can be said from that. 60% of 10 is 6. 60% of 100 is 60 and so on.
2)Only total number of scoops served is given. It can be 50 ppl double scoop, 20 ppl single scoop or 40 ppl double scoop, 40 ppl single scoop and so on.

1 & 2 together

2*.6*x + 1*.4*x = 120

One equation, one unknown. Easily solvable. Hence answer is C

1.6*x = 120

x = 75

So. no. of ppl to whom double scoop was served = .6*75 = 45
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Re: At a certain picnic, each of the guests was served either a [#permalink]

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15 Oct 2012, 13:51
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without any calculation we can solve DS (in this precise scenario)

To have a solution we need total of the guests AND a % or a ratio or something to make the information manageable. otherwise we can't solve

1) we have a % but nothing else. insuff

2) we have the total but nothing else. insuff

Together we have what we are looking for C $$must$$ be the answer

We could save precious seconds for other questions, tougher.
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16 Oct 2012, 04:22
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statement one we know the following
double scoop = 0.60 X
single scoop = 0.40 X
no other information insufficient

statement 2
we are given the total and no other info again insufficient

combining 1 and 2

2*0.60X +0.40X = 120
1.20X +0.40X = 120
1.60X = 120
x=120/1.6 = 75

sufficient we didn't need to do the above steps we know there was 1 unknown and 1 equation

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Re: At a certain picnic, each of the guests was served either a [#permalink]

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16 Oct 2012, 05:19
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Statement 1:
Double scoop , D = 60% of Total, T
=> Single scoop, S= 40% of T
=> D/S=3/2

and D+S =T
Not suff to find T.

Statement 2:
2D +S =120
Not suff to find T.

However combining two statements we have 2 equations to find S and D. And hence we can find T.
Ans C.

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At a certain picnic, each of the guests was served either a single scoop or a double scoop of ice cream. How many of the guests were served a double scoop of ice cream?

(1) At the picnic, 60 percent of the guests were served a double scoop of ice cream.
(2) A total of 120 scoops of ice cream were served to all the guests at the picnic.

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Question: 61
Page: 280
Difficulty: 600

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Re: At a certain picnic, each of the guests was served either a [#permalink]

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16 Oct 2012, 11:18
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120*.60 is out ans..

its C..
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19 Oct 2012, 04:07
SOLUTION

At a certain picnic, each of the guests was served either a single scoop or a double scoop ice-cream. How many of the guests were served a double scoop of ice-cream?

(1) At the picnic, 60 percent of the guests were served a double scoop of ice-cream --> $$\frac{x}{y}=\frac{4}{6}=\frac{2}{3}$$, where $$x$$ is the # of people served single scoop and $$y$$ the # of people served double scoop. Clearly insufficient to calculate single numerical value of $$y$$.

(2) A total of 120 scoops of ice-cream were served to all the guests at the picnic --> $$1*x+2*y=120$$. Again not sufficient.

(1)+(2) $$x=\frac{2}{3}y$$ and $$x+2y=120$$: we have 2 distinct linear equations with 2 unknowns, hence we can solve for $$x$$ and $$y$$. Sufficient. (Just to illustrate: $$\frac{2}{3}y+2y=120$$ --> $$y=45$$)

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Re: At a certain picnic, each of the guests was served either a [#permalink]

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23 Oct 2013, 04:25
What is the problem with my equation? What did I miss?
A) Is clearly insufficient
But for B) I tried this: 120 = 2*(0,6*x)+1*(0,4*x)
With x being the # of people who had ice cream.
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Re: At a certain picnic, each of the guests was served either a [#permalink]

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23 Oct 2013, 05:49
Marcoson wrote:
What is the problem with my equation? What did I miss?
A) Is clearly insufficient
But for B) I tried this: 120 = 2*(0,6*x)+1*(0,4*x)
With x being the # of people who had ice cream.

You used info given in the first statement for the second statement.
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Re: At a certain picnic, each of the guests was served either a [#permalink]

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23 Oct 2013, 06:25
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Yes, thank you. I was lacking in concentration.
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Re: At a certain picnic, each of the guests was served either a [#permalink]

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04 Feb 2014, 17:20
What if there was 100 people at the party, then 60 people get a double scoop (so 120 scoops are given out), and 0 people get single scoops? Based on this my answer was E since the problem states that people are served EITHER a single scoop OR double scoop. How can you answer this question without knowing how many people are at the party?
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Re: At a certain picnic, each of the guests was served either a [#permalink]

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05 Feb 2014, 00:43
HCalum11 wrote:
What if there was 100 people at the party, then 60 people get a double scoop (so 120 scoops are given out), and 0 people get single scoops? Based on this my answer was E since the problem states that people are served EITHER a single scoop OR double scoop. How can you answer this question without knowing how many people are at the party?

This case is not possible because it violates info given in the stem: each of the guests was served either a single scoop or a double scoop ice-cream.

As for the # of the guests, we can get it when we combine the statements:
30 of the guests were served a single scoop of ice-cream;
45 of the guests were served a double scoop of ice-cream.

Total = 30 + 45 = 75 guests.

For more check here: at-a-certain-picnic-each-of-the-guests-was-served-either-a-140734.html#p1131491

Hope it helps.
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08 Feb 2015, 17:21
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At a certain picnic, each of the guests was served either a [#permalink]

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24 May 2015, 03:06
First theory (from MGMAT)

Concrete value
If a Data Sufficiency question asks for the concrete value of one element of a ratio, you will need
BOTH the concrete value of another element of the ratio AND the relative value of two elements
of the ratio.

Relative value
If a Data Sufficiency question asks for the relative value of two pieces of a ratio, ANY statement
that gives the relative value of ANY two pieces of the ratio will be sufficient.

We can solve this question using ratios
D= # of double-Scoop portions served
T= # Total portions served

(1) At the picnic, 60 percent of the guests were served a double scoop of ice cream.
This statement tells us that the ratio of D/T = 3/5 Not Sufficient (See explanation above - we are asked to find the concrete Value)

(2) A total of 120 scoops of ice cream were served to all the guests at the picnic.
Not sufficient because we need add. a ratio od D/T to answer this question

(1+2) D/S = 3/5 so we have 3x+5x = 120
X = 15 --> D=3*15 =45 (C) Correct, can be calculated, BUT if you know the theory you don't need to calculate by DS Questions, it's enoough to know whether it can be calculated or not.

Hope this helps
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27 Jun 2016, 23:20
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Re: At a certain picnic, each of the guests was served either a [#permalink]

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07 Jan 2017, 15:44
Why not do:

1)3/5(total)=double

2)total=120

1)+2) sufficient.

Am I oversimplifying this?
Re: At a certain picnic, each of the guests was served either a   [#permalink] 07 Jan 2017, 15:44
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