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GMAT PREP 1 Question what is the remainder

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Source: — Data Sufficiency |
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by Zipper » Sun Dec 07, 2008 10:13 am
Sure,

question: 3^(4n+2)+m/10=? remainder
4n+2= 6,10,14,18 always 4 apart so 3^(4n+2)/10= always remainder 9.

1. n=2

Nothing new we know already that for every n the unit's digit is 9. We know nothing about m so //insuff

2. m=1

3^(4n+2)+1= 0 unit's digit so remainder = 0 //suff

Hence, B

Don't have much time atm so if you still have any questions replay. I will do my best to answer it in more detail after a dinner.
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by cramya » Sun Dec 07, 2008 10:15 am
It should be B)


Stmt I

n=2

3^4(2)+2 = 3^10 will have units digit 9

If m=1 then the 9+1 the units digit of the resulting number will be 0 and therefore divisible by 10
If m=2 then the remiander will be 1

Any remiander value from 0 to 9 possible depending on the value of m
INSUFF


Stmt II

m=1

3^(4n+2) will have unbits digit of 9 always for n=1,2,3.... so really we dont need the balue of n. All we need is one defniite value for m which is given to be 1

If m=1 then the 9+1 the units digit of the resulting number will be 0 and therefore divisible by 10

SUFF


Choose B)
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by cramya » Sun Dec 07, 2008 10:16 am
Units digit iof 3 cycle as follows

3,9,7,1,3,9,7,1,3,9,7,1..... so on
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by poonam1279 » Sun Dec 07, 2008 11:21 am
Many Thanks Cramya and zipper
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by hwiya320 » Sun Dec 07, 2008 3:02 pm
cramya wrote:Units digit iof 3 cycle as follows

3,9,7,1,3,9,7,1,3,9,7,1..... so on
if the pattern is different, how is the unit digit is when divided by 10?

I'm confused.
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by cramya » Sun Dec 07, 2008 3:46 pm
if the pattern is different, how is the unit digit is when divided by 10?

I'm confused.
The pattern is the same it repeats as follows

3,9,7,1,3,9,7,1,3,9,7,1,3,9,7,1,

if n=1 4n+2 is 6
if n=2 4n+2 is 10

As u can see for n=3,4... 4n+2 value changes but the units digit always is 9

We really dont need n(givenj as positive integer cant be 0 so we start with 1) as we can substitute1,2,3 etc... Hence we need just m to get to one defnite answer

Hope this helps! Let me know if u still hv questions.
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