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What is the remainder when positive integer x is divided by

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What is the remainder when positive integer x is divided by  [#permalink]

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New post 05 Mar 2013, 08:11
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What is the remainder when positive integer x is divided by 3?

(1) When x is divided by 6, the remainder is 2
(2) When x is divided by 15, the remainder is 2


What's a good approach to a problem like this. This was the first problem I got on my OG Test

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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 06 Mar 2013, 01:48
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What is the remainder when positive integer x is divided by 3?

(1) When x is divided by 6, the remainder is 2 --> \(x=6q+2=3(2q)+2\) --> the remainder upon division x by 3 is 2. Sufficient.

(2) When x is divided by 15, the remainder is 2 --> \(x=15p+2=3(5p)+2\) --> the remainder upon division x by 3 is 2. Sufficient.

Answer: D.

For more on remainders check here: remainders-144665.html

Hope it helps.
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 05 Mar 2013, 09:47
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manimgoindowndown wrote:
What is the remainder when positive integer x is divided by 3?
1) When x is divided by 6, the remainder is 2
2) When x is divided by 15, the remainder is 2




From F.S 1, we have that x = 6k+2, where k is a non-negative integer constant. Required to find x = 3p+r, where p= again a non-negative integer constant. We can see that for some value, 6k =\(3*(2k)\) = 3p. Thus, the remainder when divided by 3 will also be 2. Sufficient.

Similarly, from F.S 2 , we have that x = 15t+2. Just as above, for some integer, 15t = \(3*(5t)\) = 3p. Thus, the remainder is 2.Sufficient.

D.
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 06 Mar 2013, 05:45
Bunuel wrote:
What is the remainder when positive integer x is divided by 3?

(1) When x is divided by 6, the remainder is 2 --> \(x=6q+2=3(2q)+2\) --> the remainder upon division x by 3 is 2. Sufficient.

(2) When x is divided by 15, the remainder is 2 --> \(x=15p+2=3(5p)+2\) --> the remainder upon division x by 3 is 2. Sufficient.

Answer: D.

For more on remainders check here: remainders-144665.html

Hope it helps.

Thanks even though it's my off day I'm going to run through that thread. Thanks for sorting the problems by difficulty. Your work and its contribution has been immense to my preparation Bunuel
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 06 Feb 2015, 01:41
Quote:
(1) When x is divided by 6, the remainder is 2 --> x=6q+2=3(2q)+2 --> the remainder upon division x by 3 is 2. Sufficient.

(2) When x is divided by 15, the remainder is 2 --> x=15p+2=3(5p)+2 --> the remainder upon division x by 3 is 2. Sufficient.

Answer: D.


I am a little bit confused even though its just a simple problem.

My remainder formula is : x/y = x/y + r/y where R is the remainder ...

any one able to help me out ? Sorry !
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 06 Feb 2015, 04:08
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sauberheine1 wrote:
Quote:
(1) When x is divided by 6, the remainder is 2 --> x=6q+2=3(2q)+2 --> the remainder upon division x by 3 is 2. Sufficient.

(2) When x is divided by 15, the remainder is 2 --> x=15p+2=3(5p)+2 --> the remainder upon division x by 3 is 2. Sufficient.

Answer: D.


I am a little bit confused even though its just a simple problem.

My remainder formula is : x/y = x/y + r/y where R is the remainder ...

any one able to help me out ? Sorry !


Check here: remainders-144665.html

If \(x\) and \(y\) are positive integers, there exist unique integers \(q\) and \(r\), called the quotient and remainder, respectively, such that \(y =divisor*quotient+remainder= xq + r\) and \(0\leq{r}<x\).

For example, when 15 is divided by 6, the quotient is 2 and the remainder is 3 since \(15 = 6*2 + 3\).

Notice that \(0\leq{r}<x\) means that remainder is a non-negative integer and always less than divisor.

This formula can also be written as \(\frac{y}{x} = q + \frac{r}{x}\).
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 06 Feb 2015, 10:53
aaahhh good lord ! Now I got it ! Thanks a lot...

sry for my confusion...
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 06 Feb 2015, 12:04
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Hi All,

These types of 'remainder' questions are almost always easily solved by TESTing VALUES.

We're told that X is a positive integer. We're asked for the remainder when X is divided by 3.

Fact 1: When X is divided by 6, the remainder is 2

I'm going to list out the first few integers that fit this description:

X = 2, 8, 14, 20, 26, 32, etc....

The pattern here is that each number is "6 more" than the one before it. Now, let's see what happens when we use these values in the question:

IF...
X = 2
2/3 = 0 remainder 2

X = 8
8/3 = 2 remainder 2

X = 14
14/3 = 4 remainder 2

X = 20
20/3 = 6 remainder 2
Etc.

The pattern here is clear (and you could probably name the next few "results" without doing any calculations at all). The remainder is ALWAYS 2.
Fact 1 is SUFFCIENT

Fact 2: When X is divided by 15, the remainder is 2

Here are the first few terms that fit this Fact:

X = 2, 17, 32, 47, etc.

IF....
X = 2
2/3 = 0 remainder 2

X = 17
17/3 = 5 remainder 2

X = 32
32/3 = 10 remainder 2

X = 47
47/3 = 15 remainder 2
Etc.

Just as in Fact 1, we have a clear pattern here. The answer is ALWAYS 2.
Fact 2 is SUFFICIENT

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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 21 Oct 2017, 02:35
Question says, X=3p + r (we need to find the value of r )

(1) says, X=6a+2 => X=3*2a+2 => X=3b+2, comparing with original equation, it is SUFFICIENT

(2) says, X=15f+2 => X=3*5g+2 => X=3h+2, comparing with original equation, it is SUFFICIENT

Answer is – D.
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What is the remainder when positive integer x is divided by  [#permalink]

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New post 22 Jul 2018, 18:56
EMPOWERgmatRichC niks18 chetan2u amanvermagmat gmatbusters KarishmaB

Do you have any strategy for picking numbers? I tried two random numbers when I got this Q in my mock and was lucky to get through.
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 22 Jul 2018, 20:25
adkikani wrote:
EMPOWERgmatRichC niks18 chetan2u amanvermagmat gmatbusters KarishmaB

Do you have any strategy for picking numbers? I tried two random numbers when I got this Q in my mock and was lucky to get through.


Hi adkikani

the algebraic approach has already been explained by Bunuel here

https://gmatclub.com/forum/what-is-the- ... l#p1192221
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 23 Jul 2018, 03:55
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adkikani wrote:
EMPOWERgmatRichC niks18 chetan2u amanvermagmat gmatbusters KarishmaB

Do you have any strategy for picking numbers? I tried two random numbers when I got this Q in my mock and was lucky to get through.



Number picking is not a good idea here. If you do want to use it, you need to find the repeating pattern.
Here, every number you take that satisfies either stmnt, you will get the same answer.

But say, stmnt 1 was
(1) When x is divided by 5, the remainder is 2.
So in case of 7, when you divide by 3, you will get 1.
In case of 12, when you divide by 3, you will get 0.
In case of 17, when you divide by 3, you will get 2.
In case of 22, when you divide by 3, you will get 1.
In case of 27, when you divide by 3, you will get 0.
so you see a pattern and all your cases are covered.

Much better would be to look at this from a holistic angle. Check here:
https://www.veritasprep.com/blog/2011/0 ... unraveled/
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Re: What is the remainder when positive integer x is divided by  [#permalink]

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New post 28 Jul 2018, 02:28
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KarishmaB wrote:
adkikani wrote:
EMPOWERgmatRichC niks18 chetan2u amanvermagmat gmatbusters KarishmaB

Do you have any strategy for picking numbers? I tried two random numbers when I got this Q in my mock and was lucky to get through.



Number picking is not a good idea here. If you do want to use it, you need to find the repeating pattern.
Here, every number you take that satisfies either stmnt, you will get the same answer.

But say, stmnt 1 was
(1) When x is divided by 5, the remainder is 2.
So in case of 7, when you divide by 3, you will get 1.
In case of 12, when you divide by 3, you will get 0.
In case of 17, when you divide by 3, you will get 2.
In case of 22, when you divide by 3, you will get 1.
In case of 27, when you divide by 3, you will get 0.
so you see a pattern and all your cases are covered.

Much better would be to look at this from a holistic angle. Check here:
https://www.veritasprep.com/blog/2011/0 ... unraveled/


Hello KarishmaB, as a general rule or with practise, I don't even need to find a pattern, I would try to save as much time as possible. If the question would have been a little different suppose, I wanted remained when same number is divided by 11.

I can see when divided by 6 leaves a remainder of 2, when divided by 15 same remainder. i would just take LCM of both and add the remainder which will give me value of N.

LCM is 30 and N is 30+2. This came to me with practise. So coming back to divisibility by 3. Rem is 2 , by 7 it would be 4.

Pattern approach is important to come to understanding my approach. Kudos for explaining basics.
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Re: What is the remainder when positive integer x is divided by &nbs [#permalink] 28 Jul 2018, 02:28
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