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10! + 9! can be rewritten as:

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Bunuel
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10! + 9! can be rewritten as: [#permalink] New post  25 Apr 2017, 01:16
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10! + 9! can be rewritten as:

A. 9!(10)
B. 11!/10
C. (10!)^2*9
D. (9!)^2 + 10
E. 19!
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BrentGMATPrepNow
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Re: 10! + 9! can be rewritten as: [#permalink] New post  07 Mar 2018, 09:16
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Bunuel wrote:
10! + 9! can be rewritten as:

A. 9!(10)
B. 11!/10
C. (10!)^2*9
D. (9!)^2 + 10
E. 19!


First recognize that 10! = (10)(9!)
Here's why:
10! = (10)(9)(8)(7)(6)(5)(4)(3)(2)(1)
= (10)(9!)

So....
10! + 9! = (10)(9!) + 9!
= 9!(10 + 1) [I factored out the 9!]
= 9!(11)
Check the answer choice.....9!(11) isn't there! So, we'll need to check each answer choice to see which one can be expressed as (9!)(11)



A. 9!(10)
We can clearly see that this is not equal to (9!)(11)
ELIMINATE A


B. 11!/10
11!/10 = (11)(10)(9)(8)(7)(6)(5)(4)(3)(2)(1)/(10)
= (11)(9)(8)(7)(6)(5)(4)(3)(2)(1)
= (11)(9!) PERFECT!!
= B

Cheers,
Brent
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sandeepb17
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Re: 10! + 9! can be rewritten as: [#permalink] New post  25 Apr 2017, 01:27
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10! + 9!
= (10*9!)+ 9!
=9! (10+1)
=9!(11)
=(9!*11*10)/10
=11!/10

Hence B

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JeffTargetTestPrep
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Re: 10! + 9! can be rewritten as: [#permalink] New post  12 Mar 2018, 09:55
Expert Reply
Bunuel wrote:
10! + 9! can be rewritten as:

A. 9!(10)
B. 11!/10
C. (10!)^2*9
D. (9!)^2 + 10
E. 19!


10! + 9! = 10 x 9! + 9! = 9!(10 + 1) = 9!(11) = 11!/10

Answer: B
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Re: 10! + 9! can be rewritten as: [#permalink] New post  28 Jun 2022, 03:12
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: 10! + 9! can be rewritten as: [#permalink]
28 Jun 2022, 03:12
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