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GMAT PREP QUES?

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GMAT PREP QUES?

by dferm » Tue Mar 18, 2008 5:42 pm
THE VALUE OF 10^8 - 10^2/10^7 - 10^3 is closest to which of the following?

A. 1
B. 10
C. 10^2
D. 10^3
E. 10^4

PLEASE EXPLAIN.....
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Re: GMAT PREP QUES?

by Stuart@KaplanGMAT » Tue Mar 18, 2008 7:19 pm
dferm wrote:THE VALUE OF 10^8 - 10^2/10^7 - 10^3 is closest to which of the following?

A. 1
B. 10
C. 10^2
D. 10^3
E. 10^4

PLEASE EXPLAIN.....
I'm assuming that this is one big division problem and should read:

(10^8 - 10^2)/(10^7 - 10^3)

(because otherwise none of the answers make sense).

If you understand powers of 10, this is a VERY quick question.

10^8 is MUCH bigger than 10^2. In fact, it's so much bigger that 10^8 - 10^2 is pretty much just 10^8.

Similarly, 10^7 - 10^3 is really just 10^7.

So, the question really is:

what's the value of 10^8/10^7, which equals 10^1: choose (b).
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by siddarthd2919 » Tue Mar 18, 2008 7:28 pm
i am not sure of this method correct me if i am wrong

take log on both sides we get==== (8-2)/(7-3) =3/2......now taking antilog on both sides we get 10^(3-2) = 10 :D
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by JorgeStevenson » Wed Mar 19, 2008 12:10 am
To the guy above me:

You can't take the log of the numerator and denominator of a fraction and have it equal the same thing:

2/1 = 2

But log(2)/log(1) = undefined

100/10 = 10

But log(100)/log(10) = 2


Trust me dude I had to learn that one the hard way...good luck on the test yall.
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