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Positive integer n leaves a remainder of 4 after division by

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Re: Manhattan Remainder Problem [#permalink] New post 03 Nov 2012, 13:14
Bunuel wrote:
To elaborate more.

Suppose we are told that:
Positive integer n leaves a remainder of 4 after division by 6 and a remainder of 2 after division by 8. What is the remainder that n leaves after division by 12?

The statement "positive integer n leaves a remainder of 4 after division by 6" can be expressed as: n=6p+4. Thus according to this particular statement n could take the following values: 4, 10, 16, 22, 28, 34, 40, 46, 52, 58, 64, ...

The statement "positive integer n leaves a remainder of 2 after division by 8" can be expressed as: n=8q+2. Thus according to this particular statement n could take the following values: 2, 10, 18, 26, 34, 42, 50, 58, 66, ...

The above two statements are both true, which means that the only valid values of n are the values which are common in both patterns. For example n can not be 16 (from first pattern) as the second formula does not give us 16 for any value of integer q.

So we should derive general formula (based on both statements) that will give us only valid values of n.

How can these two statement be expressed in one formula of a type n=kx+r? Where x is divisor and r is a remainder.

Divisor x would be the least common multiple of above two divisors 6 and 8, hence x=24.

Remainder r would be the first common integer in above two patterns, hence r=10.

Therefore general formula based on both statements is n=24k+10. Thus according to this general formula valid values of n are: 10, 34, 58, ...

Now, n divided by 12 will give us the reminder of 10 (as 24k is divisible by 12).

Hope it helps.



Hi Bunuel, I had a quick question with this explanation:

Do we have to find the LCM? I just multiplied 6 x 8 and got 48 => n = 48k + 10 which also leads to a remainder of 10.
My question is is finding the LCM necessary?
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 16 Dec 2012, 13:22
n=24k+10=12(12k)+10 --> n can be: 10, 34, 58, ... n divided by 12 will give us the reminder of 10.

As, you can see, n divided by 14 can give different remainders. If n=10, then n divided by 14 yields the remainder of 10 but if n=34, then n divided by 14 yields the remainder of 6.

Bunuel - Can you please explain this? how does 24k+10 = 12(12k)+10

and can you help me to visualize how you would divide 24k+10 by 12? thanks!
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 16 Dec 2012, 22:29
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jmuduke08 wrote:
n=24k+10=12(12k)+10 --> n can be: 10, 34, 58, ... n divided by 12 will give us the reminder of 10.

As, you can see, n divided by 14 can give different remainders. If n=10, then n divided by 14 yields the remainder of 10 but if n=34, then n divided by 14 yields the remainder of 6.

Bunuel - Can you please explain this? how does 24k+10 = 12(12k)+10

and can you help me to visualize how you would divide 24k+10 by 12? thanks!


It's n=24k+10=12*2k+10, not n=24k+10=12*12k+10.
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 18 Dec 2012, 00:40
Ans:

since n is greater than 30 we check for the number which gives a remainder of 4 after dividing by 6 and 3 after dividing by 5 , the number comes out to 58. So it will give a remainder of 28 after dividing by 30. Answer (E).
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 08 Jul 2013, 00:10
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 05 Feb 2014, 22:41
Listing the integers to obtain a common value takes time. Can this be done some other way ?
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 05 Feb 2014, 22:44
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 13 Apr 2014, 21:37
Maybe I did something wrong, or I just got lucky, so please inform me. I also had 28 as the solution, by just plugging in the values.

a. 3 / 6 = 0 r 6 INCORRECT
b. 12 / 6 = 2 r 0 INCORRECT
c. 18 / 6 = 3 r 0 INCORRECT
d. 22 / 6 = 3 r 4 & 22 / 5 = 4 r 2 INCORRECT
e. 28 / 6 = 4 r 4 & 28 / 5 = 4 r 3 CORRECT

Super-simple math, so there must be something wrong here, haha. :-D
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Re: Manhattan Remainder Problem [#permalink] New post 17 Apr 2014, 11:12
Bunuel wrote:
To elaborate more.

Suppose we are told that:
Positive integer n leaves a remainder of 4 after division by 6 and a remainder of 2 after division by 8. What is the remainder that n leaves after division by 12?

The statement "positive integer n leaves a remainder of 4 after division by 6" can be expressed as: n=6p+4. Thus according to this particular statement n could take the following values: 4, 10, 16, 22, 28, 34, 40, 46, 52, 58, 64, ...

The statement "positive integer n leaves a remainder of 2 after division by 8" can be expressed as: n=8q+2. Thus according to this particular statement n could take the following values: 2, 10, 18, 26, 34, 42, 50, 58, 66, ...

The above two statements are both true, which means that the only valid values of n are the values which are common in both patterns. For example n can not be 16 (from first pattern) as the second formula does not give us 16 for any value of integer q.

So we should derive general formula (based on both statements) that will give us only valid values of n.

How can these two statement be expressed in one formula of a type n=kx+r? Where x is divisor and r is a remainder.

Divisor x would be the least common multiple of above two divisors 6 and 8, hence x=24.

Remainder r would be the first common integer in above two patterns, hence r=10.

Therefore general formula based on both statements is n=24k+10. Thus according to this general formula valid values of n are: 10, 34, 58, ...

Now, n divided by 12 will give us the reminder of 10 (as 24k is divisible by 12).

Hope it helps.



Bunuel – very good explanation.

First case - i). given statement in a question is - Remainder is 7 when positive integer n is divided by 18. And ii). if we are asked to find out the remainder when n is divided by 6,

Then since 18 is completely divisible by 6 or 6 is a factor of 18, we can find out the solution easily by above given statement. As, n = 18 q + 7; 18 is completely divisible by 6, thus no remainder exists when 18q/6 and when 7 is divided by 6, it would yield 1 as the remainder.

Second case i). given statement in a question is - Remainder is 7 when positive integer n is divided by 18. And ii). if we are asked to find out the remainder when n is divided by 8,

Then since 18 is not divisible by 8 or 8 is not a factor of 18, we cannot find out the solution by above given statement.

Third case i). given statement in a question is - Remainder is 7 when positive integer n is divided by 6. And ii). if we are asked to find out the remainder when n is divided by 12,

Then since 6 is not divisible by 12, however it true the other way round. We cannot find out the solution by above given statement.

Fourth case, which you have explained – “Positive integer n leaves a remainder of 4 after division by 6 and a remainder of 2 after division by 8. What is the remainder that n leaves after division by 12?”

We have two given statements – since one statement will not yield us the answer as explained in my earlier three cases. But, since we have two given statements which derive – n = 6Q1 + 4 & n = 8Q2 + 2. Q1, Q2 are quotients respectively.
And if we look at 6Q1 and 8 Q2, the LCM yields 24. Since we are asked the remainder when division is done by 12 and since 12 is completely divisible by 24. Thus, we can come up with a solution. Otherwise we cannot.

I hope I was able to explain what I wanted to and the above conclusion described in the 4 cases is correct.
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Re: Manhattan Remainder Problem [#permalink] New post 18 May 2014, 11:55
Bunuel wrote:
To elaborate more.

Suppose we are told that:
Positive integer n leaves a remainder of 4 after division by 6 and a remainder of 2 after division by 8. What is the remainder that n leaves after division by 12?

The statement "positive integer n leaves a remainder of 4 after division by 6" can be expressed as: n=6p+4. Thus according to this particular statement n could take the following values: 4, 10, 16, 22, 28, 34, 40, 46, 52, 58, 64, ...

The statement "positive integer n leaves a remainder of 2 after division by 8" can be expressed as: n=8q+2. Thus according to this particular statement n could take the following values: 2, 10, 18, 26, 34, 42, 50, 58, 66, ...

The above two statements are both true, which means that the only valid values of n are the values which are common in both patterns. For example n can not be 16 (from first pattern) as the second formula does not give us 16 for any value of integer q.

So we should derive general formula (based on both statements) that will give us only valid values of n.

How can these two statement be expressed in one formula of a type n=kx+r? Where x is divisor and r is a remainder.

Divisor x would be the least common multiple of above two divisors 6 and 8, hence x=24.

Remainder r would be the first common integer in above two patterns, hence r=10.

Therefore general formula based on both statements is n=24k+10. Thus according to this general formula valid values of n are: 10, 34, 58, ...

Now, n divided by 12 will give us the reminder of 10 (as 24k is divisible by 12).
Hope it helps.


Hi Bunuel,

All of this makes sense but I would like to challenge the last statement highlighted above.

In this case, we can obviously write n=12(2k)+10 as you highlighted in the later posts. If for some reason, let's say it asked for a number that wasn't divisible by 24, wouldn't that make the equation n=24k+10 invalid? Meaning, it asked what is the remainder that n leaves after division by 11?

Additionally, what if it asked "what is the remainder that n leaves after division by 48. Could we still apply the same logic and say 10?

Thanks!
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Re: Manhattan Remainder Problem [#permalink] New post 19 May 2014, 07:00
Expert's post
russ9 wrote:
Bunuel wrote:
To elaborate more.

Suppose we are told that:
Positive integer n leaves a remainder of 4 after division by 6 and a remainder of 2 after division by 8. What is the remainder that n leaves after division by 12?

The statement "positive integer n leaves a remainder of 4 after division by 6" can be expressed as: n=6p+4. Thus according to this particular statement n could take the following values: 4, 10, 16, 22, 28, 34, 40, 46, 52, 58, 64, ...

The statement "positive integer n leaves a remainder of 2 after division by 8" can be expressed as: n=8q+2. Thus according to this particular statement n could take the following values: 2, 10, 18, 26, 34, 42, 50, 58, 66, ...

The above two statements are both true, which means that the only valid values of n are the values which are common in both patterns. For example n can not be 16 (from first pattern) as the second formula does not give us 16 for any value of integer q.

So we should derive general formula (based on both statements) that will give us only valid values of n.

How can these two statement be expressed in one formula of a type n=kx+r? Where x is divisor and r is a remainder.

Divisor x would be the least common multiple of above two divisors 6 and 8, hence x=24.

Remainder r would be the first common integer in above two patterns, hence r=10.

Therefore general formula based on both statements is n=24k+10. Thus according to this general formula valid values of n are: 10, 34, 58, ...

Now, n divided by 12 will give us the reminder of 10 (as 24k is divisible by 12).
Hope it helps.


Hi Bunuel,

All of this makes sense but I would like to challenge the last statement highlighted above.

In this case, we can obviously write n=12(2k)+10 as you highlighted in the later posts. If for some reason, let's say it asked for a number that wasn't divisible by 24, wouldn't that make the equation n=24k+10 invalid? Meaning, it asked what is the remainder that n leaves after division by 11?

Additionally, what if it asked "what is the remainder that n leaves after division by 48. Could we still apply the same logic and say 10?

Thanks!


If the question were what is the remainder when n is divided by 11, then the answer would be "cannot be determined". The same if the question asked about the remainder when n is divided by 48. See, according to this general formula valid values of n are: 10, 34, 58, ... These values give different remainders upon division by 11, or 48.
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DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: Manhattan Remainder Problem [#permalink] New post 19 May 2014, 16:55
Bunuel wrote:
russ9 wrote:
Bunuel wrote:
To elaborate more.

Suppose we are told that:
Positive integer n leaves a remainder of 4 after division by 6 and a remainder of 2 after division by 8. What is the remainder that n leaves after division by 12?

The statement "positive integer n leaves a remainder of 4 after division by 6" can be expressed as: n=6p+4. Thus according to this particular statement n could take the following values: 4, 10, 16, 22, 28, 34, 40, 46, 52, 58, 64, ...

The statement "positive integer n leaves a remainder of 2 after division by 8" can be expressed as: n=8q+2. Thus according to this particular statement n could take the following values: 2, 10, 18, 26, 34, 42, 50, 58, 66, ...

The above two statements are both true, which means that the only valid values of n are the values which are common in both patterns. For example n can not be 16 (from first pattern) as the second formula does not give us 16 for any value of integer q.

So we should derive general formula (based on both statements) that will give us only valid values of n.

How can these two statement be expressed in one formula of a type n=kx+r? Where x is divisor and r is a remainder.

Divisor x would be the least common multiple of above two divisors 6 and 8, hence x=24.

Remainder r would be the first common integer in above two patterns, hence r=10.

Therefore general formula based on both statements is n=24k+10. Thus according to this general formula valid values of n are: 10, 34, 58, ...

Now, n divided by 12 will give us the reminder of 10 (as 24k is divisible by 12).
Hope it helps.


Hi Bunuel,

All of this makes sense but I would like to challenge the last statement highlighted above.

In this case, we can obviously write n=12(2k)+10 as you highlighted in the later posts. If for some reason, let's say it asked for a number that wasn't divisible by 24, wouldn't that make the equation n=24k+10 invalid? Meaning, it asked what is the remainder that n leaves after division by 11?

Additionally, what if it asked "what is the remainder that n leaves after division by 48. Could we still apply the same logic and say 10?

Thanks!


If the question were what is the remainder when n is divided by 11, then the answer would be "cannot be determined". The same if the question asked about the remainder when n is divided by 48. See, according to this general formula valid values of n are: 10, 34, 58, ... These values give different remainders upon division by 11, or 48.


Makes complete sense. Thanks.
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Re: Positive integer n leaves a remainder of 4 after division by [#permalink] New post 31 May 2014, 13:12
Hi,
Probably a silly question....
But can some one explain why Remainder r would be the first common integer in the two patterns
n=6p+4
n=5q+3

Many Thanks
Re: Positive integer n leaves a remainder of 4 after division by   [#permalink] 31 May 2014, 13:12
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