prime numbers

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prime numbers

by lukaswelker » Tue Apr 01, 2014 1:55 am
the question is:

If p is a prime number greater than 2, what is the value of p?

(1) There are a total of 100 prime numbers between 1 and p+1
(2) there are a total of p prime numbers between 1 and 3912

How can it be (A)?

Many thanks
Lukas

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by GMATGuruNY » Tue Apr 01, 2014 3:04 am
If p is a prime number greater than 2, what is the value of p ?

(1) There are a total of 100 prime numbers between 1 and p+1

(2) There are a total of p prime numbers between 1 and 3912
Statement 1: There are a total of 100 prime numbers between 1 and p+1
1, 2, 3, 5....p, p+1.
The values in red constitute the prime numbers between 1 and p+1.
Since there are a total of 100 prime numbers between 1 and p+1, p must be the 100th prime number.
Thus, the value of p can be determined.
SUFFICIENT.

Statement 2: There are a total of p prime numbers between 1 and 3912
Here, we can determine the value of p simply by counting the number of prime numbers between 1 and 3912.
SUFFICIENT.

The correct answer is D.
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