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Re: If p is prime number, which of the following statements must be true? [#permalink]
1. Let p =2 implies (p+3)(p+5)(p+9) implies odd number and is NOT divisible by 8, reject 1.
2. Let p = 3 implies (6p+1)(6p-1) = 19*17 NOT divisible by 6, reject 2.

Ans should be B since "none of the above" is not an option. No need to check for 3rd statement.
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Re: If p is prime number, which of the following statements must be true? [#permalink]
If p is prime number, which of the following statements must be true?

I. (p + 3)*(p + 5)*(p + 9) must be divisible by 8
if p=2, not divisible by 8. not must be true.
II. (6p + 1)*(6p – 1) must be divisible by 6
if p=2, not divisible by 6. not must be true.

III. (p2 – p)*(p + 1) must be divisible by 3
=p(p-1)(p+1)
= the product of three consecutive numbers. always divisible by 3. ( p ≥ 2)
must be true.

correct answer is B
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Re: If p is prime number, which of the following statements must be true? [#permalink]
Ans: B
p is prime number
I. (p + 3)*(p + 5)*(p + 9) must be divisible by 8
putting p=2, 5*7*11..not divisible by 8...I is wrong

II. (6p + 1)*(6p – 1) must be divisible by 6
putting p=2,13*11..not divisible by 6..II is wrong

III. (p2 – p)*(p + 1) must be divisible by 3
p(p-1)(p+1) or (p-1)p(p+1)
now all numbers are consecutive, so it must be divisible by 3....III is correct
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Re: If p is prime number, which of the following statements must be true? [#permalink]
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Re: If p is prime number, which of the following statements must be true? [#permalink]
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