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If S is the infinite sequence S1=9 S2=99 S3=999 SK=10^k-1 [#permalink]
19 Feb 2012, 09:50

3

This post received KUDOS

Expert's post

morya003 wrote:

If S is the infinite sequence: S1=9, S2=99, S3=999, ..., SK = 10^K-1, ..., is every term in S divisible by the prime number p?

(1) p is greater than 2.

(2) At least one term in sequence S is divisible by p.

I think with statement 2 - if P is 3 then all the terms in the sequence are divisible by P So my answer is B

Please advise.

No, B is not correct. It's straight E: if p=3 then every term in S is divisible by p but if p=11 then some terms in S are divisible by p (for example 99 and 9999) and some are not (for example 9 and 999). Not sufficient.

Re: If S is the infinite sequence S1=9 S2=99 S3=999 SK=10^k-1 [#permalink]
22 Jan 2013, 07:24

Expert's post

fozzzy wrote:

If you were to test examples to satisfy the equations what would they be examples for each statement.

Since the answer is E, then the examples given in my post to show that the two statements taken together are not sufficient to answer the question, would also serve to discard each statement. _________________

Re: If S is the infinite sequence S1=9 S2=99 S3=999 SK=10^k-1 [#permalink]
22 Dec 2013, 06:01

Bunuel wrote:

morya003 wrote:

If S is the infinite sequence: S1=9, S2=99, S3=999, ..., SK = 10^K-1, ..., is every term in S divisible by the prime number p?

(1) p is greater than 2.

(2) At least one term in sequence S is divisible by p.

No, B is not correct. It's straight E: if p=3 then every term in S is divisible by p but if p=11 then some terms in S are divisible by p (for example 99 and 9999) and some are not (for example 9 and 999). Not sufficient.

Answer: E.

hope it's clear.

Hello Bunuel

I have a doubt here. Since we know after combining the 2 statements that the Prime number will NOT be 3 but any other Prime number that divides at least 1 number in the sequence. So now we know for SURE that EVERY TERM IS NOT Divisible by a particular Prime number( Which the Questions asks). 11 will also not divide all terms but few only.

SO should the Answer not be "C" ? Please correct me.

Re: If S is the infinite sequence S1=9 S2=99 S3=999 SK=10^k-1 [#permalink]
22 Dec 2013, 06:05

Expert's post

niyantg wrote:

Bunuel wrote:

morya003 wrote:

If S is the infinite sequence: S1=9, S2=99, S3=999, ..., SK = 10^K-1, ..., is every term in S divisible by the prime number p?

(1) p is greater than 2.

(2) At least one term in sequence S is divisible by p.

No, B is not correct. It's straight E: if p=3 then every term in S is divisible by p but if p=11 then some terms in S are divisible by p (for example 99 and 9999) and some are not (for example 9 and 999). Not sufficient.

Answer: E.

hope it's clear.

Hello Bunuel

I have a doubt here. Since we know after combining the 2 statements that the Prime number will NOT be 3 but any other Prime number that divides at least 1 number in the sequence. So now we know for SURE that EVERY TERM IS NOT Divisible by a particular Prime number( Which the Questions asks). 11 will also not divide all terms but few only.

SO should the Answer not be "C" ? Please correct me.

Re: If S is the infinite sequence S1=9 S2=99 S3=999 SK=10^k-1 [#permalink]
23 Dec 2013, 05:03

niyantg wrote:

Bunuel wrote:

morya003 wrote:

If S is the infinite sequence: S1=9, S2=99, S3=999, ..., SK = 10^K-1, ..., is every term in S divisible by the prime number p?

(1) p is greater than 2.

(2) At least one term in sequence S is divisible by p.

No, B is not correct. It's straight E: if p=3 then every term in S is divisible by p but if p=11 then some terms in S are divisible by p (for example 99 and 9999) and some are not (for example 9 and 999). Not sufficient.

Answer: E.

hope it's clear.

Hello Bunuel

I have a doubt here. Since we know after combining the 2 statements that the Prime number will NOT be 3 but any other Prime number that divides at least 1 number in the sequence. So now we know for SURE that EVERY TERM IS NOT Divisible by a particular Prime number( Which the Questions asks). 11 will also not divide all terms but few only.

SO should the Answer not be "C" ? Please correct me.

Thankyou

Actually question is asking , is every term in S divisible by the prime number p?

S1: p is greater than 2..Means wat? it means p cud b 3 ,5,7,11. If we say 3 then ans will be yes, Bt if we say 5 then we say no. Thats why Insufficient.

S2: at least one term is divisible by p. so ans wud b 3 or 11. 3 wud be divisible by every term of S, Bt 11 cud not be divisible by first term 9, and 999 etc.

Take both statement togather. still we cant give the ans, because p cud b 3 or 11. _________________

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