10! + 9! can be rewritten as:
A. 9!(10)
B. 11!/10
C. (10!)^2*9
D. (9!)^2 + 10
E. 19!
OA is B
My approach
10! + 9!
10*9! + 9!
Taking out 9! common
9!(10 + 1)
9!(11)
Now from here i don't know how to proceed. So, i am bit stuck here. However, when i was reviewing, i played around with B
11!/10
(11 * 10 * 9!) / 10
(11)9!
Same outcome as what i got when i solved earlier, but how to get B on my first approach.
Thanks
10! + 9! can be rewritten as:
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- Brent@GMATPrepNow
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You're almost there!vinni.k wrote:10! + 9! can be rewritten as:
A. 9!(10)
B. 11!/10
C. (10!)^2*9
D. (9!)^2 + 10
E. 19!
OA is B
My approach
10! + 9!
10*9! + 9!
Taking out 9! common
9!(10 + 1)
9!(11)
Now from here i don't know how to proceed. So, i am bit stuck here. However, when i was reviewing, i played around with B
11!/10
(11 * 10 * 9!) / 10
(11)9!
Same outcome as what i got when i solved earlier, but how to get B on my first approach.
Thanks
You have (11)9!
Check the answer choice.....(11)9! isn't there! So, we'll need to check each answer choice.
A. 9!(10)
We can clearly see that this is not equal to (11)9!
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!)
= B
Cheers,
Brent
- vinni.k
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Thanks Brent,Brent@GMATPrepNow wrote:
You're almost there!
You have (11)9!
Check the answer choice.....(11)9! isn't there! So, we'll need to check each answer choice.
So, the right approach for this question is to check each of the answer choices.
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
Once you've rewritten 10! + 9! as (11)9! and discovered that your answer is not among the answer choices, you can EITHER try to rewrite (11)9! so that it matches one of the answer choices, OR you can try to rewrite each answer choice so that it matches (11)9!.vinni.k wrote:Thanks Brent,Brent@GMATPrepNow wrote:
You're almost there!
You have (11)9!
Check the answer choice.....(11)9! isn't there! So, we'll need to check each answer choice.
So, the right approach for this question is to check each of the answer choices.
The second option is most likely the faster approach.
Cheers,
Brent
GMAT/MBA Expert
- Jeff@TargetTestPrep
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10! + 9! = 10 x 9! + 9! = 9!(10 + 1) = 9!(11) = 11!/10vinni.k wrote:10! + 9! can be rewritten as:
A. 9!(10)
B. 11!/10
C. (10!)^2*9
D. (9!)^2 + 10
E. 19!
Answer: B
Jeffrey Miller
Head of GMAT Instruction
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