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Easy maths problem help

by GMAT? » Thu Dec 21, 2006 12:26 pm
At a picnic, each guest is served either a single or a double scoop of ice cream. How many guests are served double scoops?

1. 60% of guests are served double scoop
2. Total of 120 scoops served at the picnic

1 and 2 alone are obviously insufficient.

My method of working the problem out:

Double scoop : Single scoop = 60 : 40.

60% of 120 = 72 and 40% of 120 = 48.

Hence 72 scoops were served as double scoops. Hence number of people getting those double scoops is 72/2 = 36.

Is this the right way of working out this problem.

Thanks a lot for your help,
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Re: Easy maths problem help

by aim-wsc » Thu Dec 21, 2006 11:06 pm
GMAT? wrote:
Hence 72 scoops were served as double scoops. Hence number of people getting those double scoops is 72/2 = 36.
YOur approach is right.
but then why you divided 72 by 2?

its not necessary... :?
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Easy maths problem help

by redh » Wed Feb 07, 2007 9:35 am
Just a remark rising Gmat star ...I am not a native speaker so the scoop thing got me confused at first

I think that the question considers the same as ONE scoop irrelevant of either it being a SINGLE or a DOUBLE scoop. For example 1 single scoop + 2 double scoops DOES NOT equal to 5 scoops but ....3 scoops!
I could be terribly wrong but just read my thought.

With this in mind,

Double scoop : Single scoop = 60 : 40.

60% of 120 = 72 and 40% of 120 = 48.

And that's it! 72 peole went with the double scoop.

THE PROBLEM with your logic was that the results were inconsistent because...

If 36 people got the double scoop then.....24 people got the single scoop (since the 36 people comprise 60% of the total people..and its either one or another way).
But you started with the thought that the single scoop was offered to 48 people. In any case it is not 36 > 48 !! So......you do not divide 72/2 ...
Lousy explanation but thats what I think


In any case since this is a Data sufficiency problem you do not need any of the extra struggle. Obviously we go for - C - as an answer.
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by Stacey Koprince » Wed Feb 07, 2007 10:27 pm
Please remember to post your source when you post a question.

We can't say "double scoop: single scoop = 60%:40%" and then use the 120 scoops to calculate off of that, because the 60:40 doesn't refer to the number of scoops but to the number of guests.

Instead say: for every 6 "double scoop" guests, we have 4 "single scoop" guests, or a ratio of 6:4. We can label those 6x and 4x respectively (x is the common multiplier). We can create an equation with the two statements:
(6x*2) + (4x*1) = 120
6x guests times 2 scoops each plus 4x guests times one scoop each equals a total of 120 scoops.

Solve for x. (Though you can stop here since this is DS.) x = 7.5 and 6*7.5 = 45. Check the math: 45 guests with two scoops each = 90 scoops. 4*7.5 = 30 guests with one scoop each = 30 scoops. 30+90 = 120.

Not the greatest question b/c you can make a fairly significant mistake (equating scoops and guests) and still get the right answer.
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by uptowngirl92 » Wed Sep 30, 2009 6:29 am
hmm.pretty surprised..I somehow remember seeing a diff. solution somewhere..anyways this is an OG question so the OA C must be correct.
IMO I got B.
Single scoop=x
Double scoop=x+x=2x
This makes stmt 2: 3x=120 making it suff..
HUh>??
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by mjsobo » Fri Oct 02, 2009 1:41 pm
uptowngirl92 wrote:hmm.pretty surprised..I somehow remember seeing a diff. solution somewhere..anyways this is an OG question so the OA C must be correct.
IMO I got B.
Single scoop=x
Double scoop=x+x=2x
This makes stmt 2: 3x=120 making it suff..
HUh>??
regardless of details of the question, we can still answer it with C using both statements. i agree that it is a poorly written question, but regardless, we can still answer it either way with C from ways posted above. you might encounter a DS question or two like this and instead of debating exactly what they are asking and worrying about a formula, if C (both) can answer the question, just move on without wasting valuable time. many times it is not necessary to figure the exact equation...with a lot of practice on DS type questions you will just be able to "eyeball" the info and move on without correctly writing out the formula.
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by money9111 » Sat Oct 03, 2009 7:28 pm
I approached the question the same was as mjsobo just stated. i could rule out the combo AD because A was insufficient. So that left BCE and since B was insufficient that obviously left C and E. I did that in about 25 seconds... at that point I hadn't done any calculations. so at that point if I had to guessed C because i knew all of the information needed to answer the question was there. didn't have to figure out what the # actually was.
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by money9111 » Sat Oct 03, 2009 7:28 pm
I approached the question the same was as mjsobo just stated. i could rule out the combo AD because A was insufficient. So that left BCE and since B was insufficient that obviously left C and E. I did that in about 25 seconds... at that point I hadn't done any calculations. so at that point if I had to guessed C because i knew all of the information needed to answer the question was there. didn't have to figure out what the # actually was.
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by money9111 » Sat Oct 03, 2009 7:32 pm
I approached the question the same was as mjsobo just stated. i could rule out the combo AD because A was insufficient. So that left BCE and since B was insufficient that obviously left C and E. I did that in about 25 seconds... at that point I hadn't done any calculations. so at that point if I had to guessed C because i knew all of the information needed to answer the question was there. didn't have to figure out what the # actually was.
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