Difficult GMAT Math Problems

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beatthegmat: Site Admin; Posts: 6778; Joined: Mon Feb 13, 2006 8:30 amFollowed by: 994 members; Location: Los Angeles, CA; Thanked: 1249 times

by beatthegmat » Sat Apr 15, 2006 2:34 pm

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.

You do not have the required permissions to view the files attached to this post.

Last edited by beatthegmat on Wed Oct 03, 2007 8:06 pm, edited 1 time in total.

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Source: Beat The GMAT — Quantitative Reasoning | Sat Apr 15, 2006 2:34 pm

isisalaska: Community Manager; Posts: 363; Joined: Sun Dec 10, 2006 12:24 pmFollowed by: 3 members; Location: St. Louis; Thanked: 7 times

Difficult GMAT Math Problems

by isisalaska » Wed Dec 13, 2006 3:43 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!

Isis Alaska

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beatthegmat: Site Admin; Posts: 6778; Joined: Mon Feb 13, 2006 8:30 amFollowed by: 994 members; Location: Los Angeles, CA; Thanked: 1249 times

Re: Difficult GMAT Math Problems

by beatthegmat » Wed Dec 13, 2006 10:43 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.

Kansonne: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Wed Jan 24, 2007 4:28 pm; Location: NJ

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!

GMAT/MBA Expert

beatthegmat: Site Admin; Posts: 6778; Joined: Mon Feb 13, 2006 8:30 amFollowed by: 994 members; Location: Los Angeles, CA; Thanked: 1249 times

Difficult GMAT Math Problems

by beatthegmat » Mon Feb 05, 2007 9:07 pm

For your reference, here's the discussion thread for this problem: https://www.beatthegmat.com/viewtopic.php?t=406

Best of luck!

art: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Wed Oct 24, 2007 9:28 am

Explanation to solution 1

by art » Wed Oct 24, 2007 11:21 am

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

ginger: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Wed Feb 20, 2008 1:07 pm

Need the File

by ginger » Wed Feb 20, 2008 1:56 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!

[email protected]

workhard_1978: Newbie | Next Rank: 10 Posts; Posts: 9; Joined: Wed Feb 27, 2008 1:01 am

by workhard_1978 » Thu Feb 28, 2008 2:33 am

Eric,

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

?

Pls let me know

jbeurg: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Sun May 25, 2008 7:41 am; Thanked: 1 times

Re: Difficult GMAT Math Problems

by jbeurg » Mon May 26, 2008 4:22 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]

wilderness: Master | Next Rank: 500 Posts; Posts: 102; Joined: Sat Mar 15, 2008 4:03 am; Thanked: 4 times

by wilderness » Fri Jul 18, 2008 5:54 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.

heathermilne: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Sun Sep 14, 2008 8:57 am; Thanked: 1 times

Updated GMAT Tough Math Probs - Answers Hidden

by heathermilne » Sat Sep 20, 2008 6:35 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.

You do not have the required permissions to view the files attached to this post.

agoyal2: Senior | Next Rank: 100 Posts; Posts: 59; Joined: Fri Feb 29, 2008 9:00 am; Thanked: 4 times

by agoyal2 » Sat May 16, 2009 7:11 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: Master | Next Rank: 500 Posts; Posts: 179; Joined: Mon Dec 29, 2008 4:41 am; Thanked: 2 times

by abhinav85 » Mon May 18, 2009 1:31 pm

Can somebody help in downloading this file.

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

NikolayZ: Master | Next Rank: 500 Posts; Posts: 124; Joined: Thu Jun 18, 2009 5:33 am; Thanked: 35 times

by NikolayZ » Fri Jun 19, 2009 1:07 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: Legendary Member; Posts: 752; Joined: Sun May 17, 2009 11:04 pm; Location: Tokyo; Thanked: 81 times; GMAT Score:680

by tohellandback » Sat Jun 20, 2009 10:12 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

The powers of two are bloody impolite!!

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