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Number Props. Chap 5. No. 9 and pgs. 68-70

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afvatcha
 Post subject: Number Props. Chap 5. No. 9 and pgs. 68-70
 Post Posted: Fri Aug 12, 2011 7:36 am 
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Course Students


Posts: 34
Hi,

I am confused about when to combine exponents through addition. Pg. 68 and 70 show examples of combining exponents using addition and then No. 9 on pg. 71 says you cant do.

pg. 68 second from the top and the bottom.

Second from top=12^5=2^10 x 3^5

I guess because 12^5= 3^5 x 4^5 so (2^10 + 3^5) x 3^4????

below it says 3^4+3^4+3^4=3^5 does it have to be three 3's for this rule to be true. for instance what would 3^4 + 3^4=


Thanks for the help!
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george.kourdin
 Post subject: Re: Number Props. Chap 5. No. 9 and pgs. 68-70
 Post Posted: Fri Aug 12, 2011 9:02 am 
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Course Students


Posts: 98
hey

maybe go back and re-read whichever chapter in the book that you are using on exponents. they typically have a table at the end that summarize all the rules. that should clear some things up.

irt your questions

12^5=2^10 x 3^5 because as you said = 12^5= 3^5 x 4^5, however, now all we do is see what else we can take the sqrt of. sqrt(4) = 2^2 so 4^5 = (2^2)^5 = 2^10...voila

i am not sure whats going on here or how you got to that number- but thats wrong.
(2^10 + 3^5) x 3^4????

3^4+3^4+3^4=3^5 - we can't combine exponents when there is addition. try to simplify. what is x+x+x? 3x. so if we have 3^4+3^4+3^4 where 3^4 term is our x then 3*(3^4) and now we can combine further because multiplication of common bases allows us to add exponents so 3*(3^4) = 3^1*3^4 = 3^5


srsly though - just go re read the summary of the exponents chapter and you are good
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jnelson0612
 Post subject: Re: Number Props. Chap 5. No. 9 and pgs. 68-70
 Post Posted: Sat Sep 17, 2011 9:46 pm 
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ManhattanGMAT Staff


Posts: 1857
George has explained things well, but please let us know if you need more help.

_________________
Jamie Nelson
ManhattanGMAT Instructor
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