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Re: composite number [#permalink]
08 Jan 2008, 06:08

5

This post received KUDOS

2

This post was BOOKMARKED

(1) The tens digit of n is a factor of the units digit of n.

If this is true then n is NOT a prime number. This is true because if the tens digit is a factor of the units digit, the whole number will be divisible by that number because the tens digit is obviously a factor of itself! Try it out:

For each of these numbers the tens digit evenly goes into itself and is then a factor of the units. Impossible to have a prime number under these rules. SUFFICIENT

2. Statement 2 tells us nothing on its own. n could be prime (23) or composite (24)

Re: composite number [#permalink]
27 Feb 2013, 03:43

1

This post was BOOKMARKED

eschn3am wrote:

(1) The tens digit of n is a factor of the units digit of n.

If this is true then n is NOT a prime number. This is true because if the tens digit is a factor of the units digit, the whole number will be divisible by that number because the tens digit is obviously a factor of itself! Try it out:

For each of these numbers the tens digit evenly goes into itself and is then a factor of the units. Impossible to have a prime number under these rules. SUFFICIENT

2. Statement 2 tells us nothing on its own. n could be prime (23) or composite (24)

Answer A

The ones in red won't satisfy the statement but the rest of the examples are spot on.. _________________

Re: composite number [#permalink]
02 Apr 2013, 08:09

fozzzy wrote:

eschn3am wrote:

(1) The tens digit of n is a factor of the units digit of n.

If this is true then n is NOT a prime number. This is true because if the tens digit is a factor of the units digit, the whole number will be divisible by that number because the tens digit is obviously a factor of itself! Try it out:

For each of these numbers the tens digit evenly goes into itself and is then a factor of the units. Impossible to have a prime number under these rules. SUFFICIENT

2. Statement 2 tells us nothing on its own. n could be prime (23) or composite (24)

Answer A

The ones in red won't satisfy the statement but the rest of the examples are spot on..

The ones in red do satisfy the statement. eschn3am is correct. EX: 2 is a factor of 6 and 8, 3 is a factor of 9

gmatclubot

Re: composite number
[#permalink]
02 Apr 2013, 08:09

Interested in applying for an MBA? In the fourth and final part of our live QA series with guest expert Chioma Isiadinso, co-founder of consultancy Expartus and former admissions...