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Exponents

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Source: — Problem Solving |

by Brent@GMATPrepNow » Mon May 20, 2013 1:56 pm
Rudy414 wrote:(10^8 - 10^2) / (10^7 - 10^3) is closest in value to which of the following?

A) 1
B) 10
C) 10^2
D) 10^3
E) 10^4
Since the answer choices are so spread out, we can be quite aggressive with our estimation.

First, 10^8 - 10^2 can be rounded to 10^8
Is this reasonable? Well, 10^8 equals 100,000,000, so subtracting 10^2 (aka 100) from 100,000,000 still leaves us with about 100,000,000

Similarly, 10^7 - 10^3 can be rounded to 10^7 (10,000,000 - 1000 is pretty close to 10,000,000)

So, by estimating, we get:
(10^8 - 10^2)/(10^7 - 10^3) = (10^8)/(10^7) [approximately]
= 10^1 = B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Matt@VeritasPrep » Mon May 20, 2013 1:58 pm
Here you go! Wrote the answer in LaTeX so the exponents are easier to read: just click on the image.


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