At a certain picnic, each of the guests was served either a

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

15 Oct 2012, 04:41

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The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

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

15 Oct 2012, 04:41

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)

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

15 Oct 2012, 05:12

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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

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

15 Oct 2012, 08:57

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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]

15 Oct 2012, 14:51

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

16 Oct 2012, 05:22

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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

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

16 Oct 2012, 06:19

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

16 Oct 2012, 12:18

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120*.60 is out ans..

its C..

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

19 Oct 2012, 05:07

Re: At a certain picnic, each of the guests was served either a [#permalink] 19 Oct 2012, 05:07

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At a certain picnic, each of the guests was served either a

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At a certain picnic, each of the guests was served either a

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