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If 0.00012345 is between 1/10^n and 1/10^{n-1}, what is the

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by Max@Math Revolution » Tue Apr 09, 2019 11:39 pm
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[GMAT math practice question]

If 0.00012345 is between 1/10^n and 1/10^{n-1}, what is the value of n?

A. 2
B. 3
C. 4
D. 5
E. 6
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If 0.00012345 is between 1/10^n and 1/10^{n-1}, what is the

by Brent@GMATPrepNow » Wed Apr 10, 2019 5:09 am
Max@Math Revolution wrote:[GMAT math practice question]

If 0.00012345 is between 1/10^n and 1/10^{n-1}, what is the value of n?

A. 2
B. 3
C. 4
D. 5
E. 6
We need to examine powers of 10 that are smaller than AND greater than 0.00012345

We know that: 0.0001 < 0.00012345 < 0.001
Rewrite as FRACTIONS to get: 1/10,000 < 0.00012345 < 1/1,000
Rewrite as POWERS OF 10 to get: 1/10� < 0.00012345 < 1/10³

We're told that 0.00012345 is between 1/10^n and 1/10^{n-1}
So, we can now see that n = 4

Answer: C

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Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Max@Math Revolution » Fri Apr 12, 2019 12:30 am
=>

0.0001 < 0.00012345 < 0.001
10^{-4} < 0.00012345 < 10^{-3}
1/10^4 < 0.00012345 < 1/10^3
Comparing this with 1/10^n < 0.00012345 < 1/10^{n-1} yields n = 4.

Therefore, the answer is C.
Answer: C
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