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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 05:32
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There are 10 letters - A, B, C, D, E, F, G, H, I J
What is the ratio of the number of 4-lettered code to the number of 5-lettered code?

(What I am curious is, do we have enough information to solve this question?)



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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 08:49
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yes, we have. use permutation, not combination because oder matters here.

so the ratio is = 10P4/10P5
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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 08:57
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In these type of questions, do we assume that letters can be replaced or not replaced?
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GMATT73
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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 09:07
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We have to assume that the letters cannot be repeated because it didn`t say so in the problem.

10P4/10P5= 1/6
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HIMALAYA
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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 09:07
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remgeo
In these type of questions, do we assume that letters can be replaced or not replaced?
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imo, repetition is not allowed, however we are not supposed to assume.
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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 09:32
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Can someone tell me how this will change if letters could be repeated in the words?
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BG
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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 09:50
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without repetition it is (10x9x8x7)/(10x9x8x7x6)=1/6
with repetition it is 10^4/10^5=1/10
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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 09:58
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remgeo
Can someone tell me how this will change if letters could be repeated in the words?
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with repetition = (10x10x10x10)/(10x10x10x10x10) =1/10
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There are 10 letters - A, B, C, D, E, F, G, H, I J What is 24 Nov 2005, 18:06
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HIMALAYA
yes, we have. use permutation, not combination because oder matters here.

so the ratio is = 10P4/10P5
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Cool. Thanks for the explanation.

10P4/10P5 is the OA.

"Use permutation when order matters"...I'll keep that in mind.

Thanks again!



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