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Difficult GMAT Math Problems

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Difficult GMAT Math Problems Post Sat Apr 15, 2006 3:34 pm
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    Here's a document with over 100 really tough GMAT math problems. If you can get through these easily, you probably don't need to prep much more for the math section.
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    Last edited by beatthegmat on Wed Oct 03, 2007 9:06 pm; edited 1 time in total

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    isisalaska Community Manager Default Avatar
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    Post Wed Dec 13, 2006 4:43 pm
    are these problems more diffcult than the ones we will find in the GMAT test? are these problems more in line iwth the Kaplan 800 book?
    Thanks!

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    Post Wed Dec 13, 2006 11:43 pm
    isisalaska wrote:
    are these problems more diffcult than the ones we will find in the GMAT test? are these problems more in line iwth the Kaplan 800 book?
    Thanks!
    These problems are overall more difficult than the ones you would encounter on the GMAT (in line with Kaplan 800). They aren't as well written as real GMAT questions, but still good practice.

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    Kansonne Just gettin' started! Default Avatar
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    Post Mon Feb 05, 2007 10:02 pm
    Hi,

    Can anyone explain the solution to the first problem in this "gmat MATH tough problems.doc" set?

    Here's the problem and solution again:

    1. The sum of the even numbers between 1 and n is 79*80, where n is an odd number, then n=?
    Sol: First term a=2, common difference d=2 since even number

    therefore sum to first n numbers of Arithmetic progression would be

    n/2(2a+(n-1)d)

    = n/2(2*2+(n-1)*2)=n(n+1) and this is equal to 79*80

    therefore n=79 which is odd...

    My questions are...

    I tried plugging and chugging different values of n into the equation above, for example, n = 3. The sum of even numbers between 1 and 3 is 2, but with the formula in the solution, I get 12. What am I doing wrong?

    Thanks!

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    Post Mon Feb 05, 2007 10:07 pm
    For your reference, here's the discussion thread for this problem: http://www.beatthegmat.com/viewtopic.php?t=406

    Best of luck!

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    art Just gettin' started! Default Avatar
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    Post Wed Oct 24, 2007 12:21 pm
    n is the number of terms in the A.P.

    For even numbers between 1 and 3 (which is 2), n is 1 and not 3
    Plug this into the formula

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    Post Wed Feb 20, 2008 2:56 pm
    Can someone please email me the file with the difficult questions? It is not opening at all and I cannot open or save it. Thanks alot!

    meermaidrose@yahoo.com Smile

    workhard_1978 Just gettin' started! Default Avatar
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    Post Thu Feb 28, 2008 3:33 am
    Eric,

    Where have these questions come from ?Kaplan,Princeton, Manhattan or OG

    ?

    Pls let me know

    jbeurg Just gettin' started! Default Avatar
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    Post Mon May 26, 2008 5:22 am
    beatthegmat wrote:
    Here's a document with over 100 really tough GMAT math problems. If you can get through these easily, you probably don't need to prep much more for the math section.
    Hi. I think there is an error in your document gmat MATH tough problems.doc. in #1, n=159, not 79. That is, 159=2n+1 is odd, using your n=79.

    Jbeurg[/quote]

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    Post Fri Jul 18, 2008 6:54 am
    Dear GMAT Gurus,

    I am taking an average of 5 minutes to solve these tough questions. I know the average time we have on GMAT is 2, but I dont expect to have many questions of this difficulty in the exam. While working with OG, my average time is less than 2 min. So the question is

    What have been your averge time when you do these questions and do you think average of 5 min per question is acceptable.

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    Post Sat Sep 20, 2008 7:35 am
    Here's another version of the same problem set, this one with the answers hidden. Print it out, solve the problems, then select all the text (CTRL+A) and turn it back to black to reveal the answers.
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    agoyal2 Rising GMAT Star Default Avatar
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    Post Sat May 16, 2009 8:11 pm
    I am looking for a solution to the below problem:

    The price of a bushel of corn is currently $3.20, and the price of a peck of wheat is $5.80. The price of corn is increasing at a constant rate of 5x cents per day while the price of wheat is decreasing at a constant rate of root(2)*x-x cents per day. What is the approximate price when a bushel of corn costs the same amount as a peck of wheat?

    Did not understand the solution presented in the document that well...

    abhinav85 Really wants to Beat The GMAT! Default Avatar
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    Post Mon May 18, 2009 2:31 pm
    Can somebody help in downloading this file.

    Its says .doc but i am unable to open it after downloading it???

    NikolayZ Really wants to Beat The GMAT! Default Avatar
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    Post Fri Jun 19, 2009 2:07 am
    agoyal2 wrote:
    I am looking for a solution to the below problem:

    The price of a bushel of corn is currently $3.20, and the price of a peck of wheat is $5.80. The price of corn is increasing at a constant rate of 5x cents per day while the price of wheat is decreasing at a constant rate of root(2)*x-x cents per day. What is the approximate price when a bushel of corn costs the same amount as a peck of wheat?

    Did not understand the solution presented in the document that well...
    Hey mate.

    Since you know the rate of both corn and wheat, you can assume that they will be equal through M days. And the differences in prices will be (rate*Mdays)

    320 + (5x*Mdays) = 580 - (.41x*Mdays), then we can combine X and days into one variable.
    I suppose you got what comes next =)

    tohellandback GMAT Destroyer! Default Avatar
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    Post Sat Jun 20, 2009 11:12 pm
    are you sure the answers are correct..I did the first problem and I think it is done wrong

    1. The sum of the even numbers between 1 and n is 79*80, where n is an odd number, then n=?
    Sol: First term a=2, common difference d=2 since even number

    therefore sum to first n numbers of Arithmetic progression would be

    n/2(2a+(n-1)d)

    = n/2(2*2+(n-1)*2)=n(n+1) and this is equal to 79*80

    therefore n=79 which is odd...
    now the n here is the number of terms in the series 2,4,6..
    the real n being asked in the question should be 79*2+1=159

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