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Fractions (/ Factorials?) Problem

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Fractions (/ Factorials?) Problem

by abduabd » Thu Feb 19, 2015 10:14 am
A friend mine who is also studying for the GMAT posted this problem in a WhatsApp group the other day. I have tried to solve this using all the tricks I know, but have come up stuck. I recognize that the denominator is essentially just consecutive [(n! - (n-3)!], but I cannot get any farther than that.

I have concluded that it cannot be a legitimate GMAT question, but, it is still bugging me that I cannot apply any of the tricks that I have learned so far to solve it.

Any ideas?

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by Brent@GMATPrepNow » Thu Feb 19, 2015 10:17 am
Do you have the answer choices available?

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by abduabd » Thu Feb 19, 2015 11:08 am
Unfortunately, Brent. I don't and neither does he. Does this look like a concept that could be tested on the GMAT, though? Is this something that can be simplified and solved in under two minutes AND without a calculator?
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by Brent@GMATPrepNow » Thu Feb 19, 2015 11:15 am
I see.

If there were answer choices, it might be possible to find a RANGE that the sum would fall into. With any luck, only one of the answer choices would fall within the calculated range.

Otherwise, I don't see a nice (GMAT-friendly) solution. I might be missing something though. Mitch?

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by GMATGuruNY » Thu Feb 19, 2015 11:20 am
The posted problem seems beyond the scope of the GMAT.
A similar problem that is more GMAT-friendly:

https://www.beatthegmat.com/sum-of-the-f ... 76078.html
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
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by Brent@GMATPrepNow » Thu Feb 19, 2015 11:23 am
Here's another one with factorials: https://www.beatthegmat.com/factorial-re ... 81604.html

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by abduabd » Thu Feb 19, 2015 12:06 pm
Thanks, Mitch and Brent. I looked at the problems you linked and I am happy that I was able to solve them.
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