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The integers r, s and t all have the same remainder when div

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The integers r, s and t all have the same remainder when div [#permalink]

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New post Updated on: 23 Sep 2013, 05:58
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The integers r, s and t all have the same remainder when divided by 5. What is the value of t?

(1) r + s = t
(2) 20 <= t <= 24

Originally posted by imhimanshu on 23 Sep 2013, 05:55.
Last edited by Bunuel on 23 Sep 2013, 05:58, edited 1 time in total.
Renamed the topic and edited the question.
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 23 Sep 2013, 06:31
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The integers r, s and t all have the same remainder when divided by 5. What is the value of t?

\(r=5a+x\)
\(s=5b+x\)
\(t=5c+x\)

Where the remainder x is \(0\leq{x}<5\).

(1) r + s = t --> \((5a+x)+(5b+x)=5c+x\) --> \(x=5(c-a-b)\) --> the remainder (x) is a multiple of 5, thus it's 0 --> r, s and t are multiples of 5. Not sufficient.

(2) 20 <= t <= 24. Clearly insufficient.

(1)+(2) There is only one multiple of 5 between 20 and 24, inclusive, namely 20. Sufficient.

Answer: C.

Hope it's clear.
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 23 Sep 2013, 07:32
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imhimanshu wrote:
The integers r, s and t all have the same remainder when divided by 5. What is the value of t?

(1) r + s = t
(2) 20 <= t <= 24


For this r,s ant t can be any values which have same remainder when divided by 5 so r=6 s=1 t=21 or r=2, s=47 and t=1002

From statement 1:
r + s = t => so for this only same remainder is "0".
But r+s=t can be any value 5+10=15 where all the numbers have remainder "0"
or 10+20=30 or etc . . .. So insufficient

From statement 2:
20<=t<=24
so t can be 20, 21,22,23,24
Hence not sufficient

From combining both the statements From 1 : r, s and t has to multiple of 5 so remainder is "0"
From 2: t = 20,21,22,23,24 so from both the multiple of 5 is 20
t=20 sufficient
hence both the statement are sufficient. answer is (c)
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 26 Dec 2013, 21:34
I still don't understand how 1) r+s = t tells us that these must be multiples of 5. (And thus the remainder is 0)

Could someone please explain? Thanks!
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 26 Dec 2013, 22:50
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rh410 wrote:
I still don't understand how 1) r+s = t tells us that these must be multiples of 5. (And thus the remainder is 0)

Could someone please explain? Thanks!


The question: when r,t,s are divided by 5, they yield the same remainder.
Remember that when X is divided by 5, the remainder must be 0,1,2,3,4 ( remainder must always be smaller than divisor)

If r and s has the same remainder, for example 1, then t can not have remainder 1 (21+11=32, remainder of the total (32) is the sum of remainders of 11 and 21, it equals 2 actually). So for the remainder to be the same, r,t and s must be multiples of 5 (20+10=30)
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 01 Dec 2014, 18:47
Bunuel wrote:
(1) r + s = t --> \((5a+x)+(5b+x)=5c+x\) --> \(x=5(c-a-b)\) .


Can someone explain these steps?

Thanks!
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 02 Dec 2014, 02:21
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 02 Dec 2014, 09:24
Bunuel wrote:
JackSparr0w wrote:
Bunuel wrote:
(1) r + s = t --> \((5a+x)+(5b+x)=5c+x\) --> \(x=5(c-a-b)\) .


Can someone explain these steps?

Thanks!


\((5a+x)+(5b+x)=5c+x\);

\(2x+5a+5b=5c+x\);

\(x=5c-5a-5b\);

\(x=5(c-a-b)\).

Hope it's clear.


Thanks, I kept getting my signs mixed up...
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The integers r, s and t all have the same remainder when div [#permalink]

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New post 12 Oct 2015, 11:11
I don't get how the answer to this is not B?

Between 20 and 24, 20 is the only number that can be comprised of numbers for which when divided by 5 give equal remainders:

Think about the numbers for t that fit in the inequality and any numbers below t that give the same remainder:

t= 20... 5, 10, 15, 20
t= 21... 6, 11, 16, 21
t= 22... 7, 12, 17, 22

and so on... The pattern becomes clear that only 20 works. What am i missing here?
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 12 Oct 2015, 21:42
dubyap wrote:
I don't get how the answer to this is not B?

Between 20 and 24, 20 is the only number that can be comprised of numbers for which when divided by 5 give equal remainders:

Think about the numbers for t that fit in the inequality and any numbers below t that give the same remainder:

t= 20... 5, 10, 15, 20
t= 21... 6, 11, 16, 21
t= 22... 7, 12, 17, 22

and so on... The pattern becomes clear that only 20 works. What am i missing here?


You are using info from (1) when evaluating (2).
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 06 Aug 2016, 15:17
Bunuel wrote:
dubyap wrote:
I don't get how the answer to this is not B?

Between 20 and 24, 20 is the only number that can be comprised of numbers for which when divided by 5 give equal remainders:

Think about the numbers for t that fit in the inequality and any numbers below t that give the same remainder:

t= 20... 5, 10, 15, 20
t= 21... 6, 11, 16, 21
t= 22... 7, 12, 17, 22

and so on... The pattern becomes clear that only 20 works. What am i missing here?


You are using info from (1) when evaluating (2).


Damn! I was so deep drilling (2) that by the time solved it I was sure I hadn't used info from (1). And I thought I was avoiding C trap!
Thanks!
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Re: The integers r, s and t all have the same remainder when div [#permalink]

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New post 29 Jan 2018, 17:46
here's the way i saw this question...

- since we're told r, s, and t all have the same remainder, it got me thinking: they would all have the same remainder if they were all multiples of 5.

(1) r+s=t
r=10, s=10, t=20. works
r=20, s=40, t=60. works
** we have 2 possible values for t, so insufficient.

(2) t is between 20 and 24
t can literally equal 20, 21, 22, 23 or 24...clearly insufficient

(3) we know t should be a multiple of 5 and within the range 20-24. there's a # here (20) that fits these 2 criteria. sufficient.
Re: The integers r, s and t all have the same remainder when div   [#permalink] 29 Jan 2018, 17:46
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