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sacmanitin
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the answer is D !! .and correction the second part of your explanation if n-m =12 ,so C(n-m,12) =C(12,12)=1 though not required to anwer . So we know that second is suff for answering ,but how is first suff for answering ?
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thats gr8 expanation ,given +1
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We need to find out (n-m)C12 = ?

From Stat 1: (n-m+1)C12 = 13 --> n-m+1 = 13 (nCn-1 = n)
so n-m = 12 --> suff
From Stat 2: n=m+12 --> n-m = 12 --> suff

Ans - D
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AKProdigy87
The answer is D.

Essentially, there is an (n-m) pool of jurors to select a group of 12 from. As a result, the number of possible juries is equivalent to \(_{(n-m)}C_{12}\), or:

\(\frac{(n-m)!}{12!*(n-m-12)!}\)

For simplicity's sake, let's set X = n - m (the pool of jurors available after processing by the defense counsel). As a result the number of possible juries is equivalent to:

\(\frac{X!}{12!*(X-12)!}\)


Statement 1: If one less potential juror had been rejected ,it would be possible to create 13 different juries:


As a result, X increases to X + 1:

\(\frac{(X+1)!}{12!*(X+1-12)!} = 13\)

\(\frac{(X+1)!}{12!*(X-11)!} = 13\)

\(\frac{(X+1)!}{(X-11)!} = 13*12!\)

\(\frac{(X+1)!}{(X-11)!} = 13!\)

\((X+1)*(X)*(X-1)*...*(X-10) = 13!\)

Therefore, by using our understanding of factorials, we can determine X (or n-m) to be 12. The answer to the original question then becomes 1, and Statement 1 is proven to be sufficient.

Statement 2: n=m+12:

Rearranging the equation sets n-m = 12, which is enough to show that the answer to the original question is 1 possible jury, and Statement 2 also proves to be sufficient.

Therefore, both statements are sufficieint by themselves, and the answer is D.

Hi, thank you for the explanation. I still have troubles understanding why the first statement is sufficient. Could you please explain what do you mean by "our understanding of factorials"? I would highly appreciate it!

Thank you!
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easy question

we actually need to find (n-m)C12 , or just value of n-m

lets start with statement 2
2)n-m=12.wow this is what we need

1)converting the expression to algebraic form:
n-m+1=13
so n-m =12
suff


D
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Can anyone please explain the statement 1 of the given question.I could not understand it.

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sacmanitin
Twelve jurors must be picked from a pool of n potential jurors .If m of the potential jurors are rejected by the defense counsel and the prosecuting attorney ,how many different possible juries could be picked from the remaining potential jurors?

(1) If one less potential juror had been rejected, it would be possible to create 13 different juries.
(2) n = m + 12

Statement One Alone:

If one fewer potential juror were rejected, it would be possible to create 13 different juries.

From statement one, we can create the equation:

(n - m + 1)C12 = 13

And we need to determine the value of (n - m)C12.

Since 13 is a prime number, the only way that (n - m + 1)C12 = 13 is if n - m + 1 = 13 (notice that 13C12 = 13). So we have n - m = 12 and thus (n - m)C12 = 12C12 = 1. Statement one alone is sufficient.

Statement Two Alone:
n = m + 12

If n = m + 12 and if m jurors did not show up, then only n - m = 12 jurors showed up. The number of ways to choose 12 jurors from 12 jurors is 12C12 = 1. Statement two alone is sufficient.

Answer: D
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