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Ice-cream scoop, Percents

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Ice-cream scoop, Percents

by anirudhbhalotia » Thu Mar 10, 2011 9:32 am
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.

OA - C[spoiler][/spoiler]
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by ankur.agrawal » Thu Mar 10, 2011 10:30 am
anirudhbhalotia wrote: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.

OA - C[spoiler][/spoiler]
Let,

N1 = No. of guests who received double scoops
N2= No. of guests who received single scoops

2N1+(N2) = 120 ---> (2)

(N1+N2)*(3/5) = N1. ---------(3)

Both Statements together are sufficient. No need to solve. :)

C
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by Night reader » Thu Mar 10, 2011 2:04 pm
@hi, anirudhbhalotia
In the order prescribed by examiner trying to catch ALL the traps!

from reading the stem we realize that there Guests- several of them, call them N (guests) and people who were served EITHER (note this math) single scoop, call them S or double scoop, call them D, of ice cream. We need to find the VALUE (so we need to solve till the END, Value/Number)

st(1) 60% were served double scoop --> 0.6N=D; since we need Value and cannot assign from 1-0.6N that 0.4N were served single scoop (S) this is Not Sufficient;
st(2) 120 scoops were served to all guests --> S+D=N This is not sufficient, as we don't know how many people were served single or double scoops - we only know that all of them were served 120 scoops;
Combined st(1&2): from statement (1) we know that 0.6N=D and from statement (2) we know S+D=N. We can write down S/D=0.6N/04.N or S/D=3/2. Since (S+D)=5 and S/(S+D)=3/5 and D(S+D)=2/5 we can deduct S/120=3/5 and D/120=2/5 or D=120*2/5, D=48; S=120*3/5=72

This is sufficient to answer the question - how many of the guests were served double scoop of the ice-cream, it's 48/2=24.
anirudhbhalotia wrote:At a certain picnic, each of the guests was served either a single scoop or a double scoop or both of ice-cream. How many of the guests were served a double scoop of ice-cream?
anirudhbhalotia wrote: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.

OA - C[spoiler][/spoiler]
Last edited by Night reader on Thu Mar 10, 2011 9:35 pm, edited 2 times in total.
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by ankur.agrawal » Thu Mar 10, 2011 7:53 pm
Night reader wrote:@hi, anirudhbhalotia
In the order prescribed by examiner trying to catch ALL the traps!

from reading the stem we realize that there Guests- several of them, call them N (guests) and people who were served EITHER (note this math) single scoop, call them S or double scoop, call them D, of ice cream. We need to find the VALUE (so we need to solve till the END, Value/Number)

st(1) 60% were served double scoop --> 0.6N=D; since we need Value and cannot assign from 1-0.6N that 0.4N were served single scoop (S) this is Not Sufficient;
st(2) 120 scoops were served to all guests --> S+D=N and because guests were not served both single And double scoop we take N=120. This is not sufficient, as we don't know how many people were served single or double scoops - we only know that all of them were served 120 scoops;
Combined st(1&2): from statement (1) we know that 0.6N=D and form statement (2) we know N=120, we can rewrite 0.6*120=D, where D=72. This is sufficient to answer the question - how many of the guests were served double scoop of the ice-cream, it's 72. You can further consider that 72 is double scoop portion and the number of people served double scoops is 72/2 in case if double scoop is Unit*2 or leave it as it's because the thing will not influence our solution - the decrease in the proportion of D should be counted in S as well.

BUT what if we had condition below changed to
anirudhbhalotia wrote:At a certain picnic, each of the guests was served either a single scoop or a double scoop or both of ice-cream. How many of the guests were served a double scoop of ice-cream?
anirudhbhalotia wrote: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.

OA - C[spoiler][/spoiler]

N= 120 ; How? Suppose 50 people got single scoop & remaining 70 got double scoop then the total no of scoops required will be 190 ( 50 + 2*70) . I am confused.

Pls split open this question for me . Its making me crazy.
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by GMATGuruNY » Thu Mar 10, 2011 8:32 pm
anirudhbhalotia wrote: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.

OA - C[spoiler][/spoiler]
Statement 1: 60% of the guests were served a double scoop
Plug in 100 guests.
60 double-scoop guests served 2 scoops each = 60*2 = 120 scoops.
40 single-scoop guests served 1 scoop each = 40*1 = 40 scoops.
Thus, the double-scoop guests were served 120/160 = 3/4 of the scoops.
No way to determine the number of double-scoop guests.
Insufficient.

Statement 2: total scoops = 120
No way to determine the number of double-scoop guests.
Insufficient.

Statements 1 and 2 combined:
The double-scoop guests were served 3/4*120 = 90 scoops.
Since each double-scoop guest received 2 scoops, double-scoop guests = 90/2 = 45.
Sufficient.

The correct answer is C.
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by Night reader » Thu Mar 10, 2011 9:15 pm
Hi, I had to revise my solution above to account not for guests BUT for scoops=120.
ankur.agrawal wrote:
N= 120 ; How? Suppose 50 people got single scoop & remaining 70 got double scoop then the total no of scoops required will be 190 ( 50 + 2*70) . I am confused.

Pls split open this question for me . Its making me crazy.
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by anirudhbhalotia » Thu Mar 10, 2011 9:48 pm
ankur.agrawal wrote:
anirudhbhalotia wrote: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.

OA - C[spoiler][/spoiler]
Let,

N1 = No. of guests who received double scoops
N2= No. of guests who received single scoops

2N1+(N2) = 120 ---> (2)

(N1+N2)*(3/5) = N1. ---------(3)

Both Statements together are sufficient. No need to solve. :)

C
This doesn't seem the right approach to me. You have to evaluate each statement...
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by anirudhbhalotia » Thu Mar 10, 2011 10:08 pm
GMATGuruNY wrote:
anirudhbhalotia wrote: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.

OA - C[spoiler][/spoiler]
Statement 1: 60% of the guests were served a double scoop
Plug in 100 guests.
60 double-scoop guests served 2 scoops each = 60*2 = 120 scoops.
40 single-scoop guests served 1 scoop each = 40*1 = 40 scoops.
Thus, the double-scoop guests were served 120/160 = 3/4 of the scoops.
No way to determine the number of double-scoop guests.
Insufficient.

Statement 2: total scoops = 120
No way to determine the number of double-scoop guests.
Insufficient.

Statements 1 and 2 combined:
The double-scoop guests were served 3/4*120 = 90 scoops.
Since each double-scoop guest received 2 scoops, double-scoop guests = 90/2 = 45.
Sufficient.

The correct answer is C.
This somehow makes sense...but here again we tend to solve it...is this the best way?

damn I hate DS...just not able to analyze and suffice! :-(
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by ankur.agrawal » Thu Mar 10, 2011 10:28 pm
anirudhbhalotia wrote:
ankur.agrawal wrote:
anirudhbhalotia wrote: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.

OA - C[spoiler][/spoiler]
Let,

N1 = No. of guests who received double scoops
N2= No. of guests who received single scoops

2N1+(N2) = 120 ---> (2)

(N1+N2)*(3/5) = N1. ---------(3)

Both Statements together are sufficient. No need to solve. :)

C
This doesn't seem the right approach to me. You have to evaluate each statement...
I think this approach is correct. On solving the two equations I get N1= 45 .

Equations (2) & (3) bring out exactly what is mentioned.

Pls point out specific mistakes in my equation. I feel it is correct. Pls correct if i have a logic gap here.
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