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Fraction factorial-mgmat

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Fraction factorial-mgmat

by joyseychow » Wed Mar 03, 2010 5:23 am
Which of the following fractions has the greatest value?


A. 3/8!

B. 6(4!) / 5(9!)

C. 4(3!) / 9!

D. 3 / 5(7!)

E. 14 / 5(8!)

Where do I start? I can't see any similarities to narrow the down the answer.
OA is D
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by harsh.champ » Wed Mar 03, 2010 5:27 am
joyseychow wrote:Which of the following fractions has the greatest value?


A. 3/8! = 3 x 9 / 9!

B. 6(4!) / 5(9!) = ((6 x 4!)/5)/9!


C. 4(3!) / 9! = 4!/9!

D. 3 / 5(7!) = (3 x 8 x 9 /5)/9!

E. 14 / 5(8!) = ((14 x 9)/5)/9!

Where do I start? I can't see any similarities to narrow the down the answer.
OA is D
Create 9! IN THE DENOMINATORS.(since it is the highest denom. in the ques.)
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by kstv » Wed Mar 03, 2010 6:18 am
The denominator can be manipulated to become 9! 8! or 7!. Then the common denominator can be cancelled.
Infact I made it 8!
And it is solvable.
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by harsh.champ » Wed Mar 03, 2010 6:21 am
kstv wrote:The denominator can be manipulated to become 9! 8! or 7!. Then the common denominator can be cancelled.
Infact I made it 8!
And it is solvable.
Yeah,surely.
I took 9! because I find multiplication easier than division. :)
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by kstv » Wed Mar 03, 2010 6:33 am
And technically we should find the LCM of the denominators which is closer to 9!.
But in under 2 mins the aim is to quickly get rid of the factorial in the denominator.
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