Problem solving

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Noman: Junior | Next Rank: 30 Posts; Posts: 17; Joined: Thu May 21, 2015 9:06 amFollowed by: 1 member

by Noman » Sat Jan 23, 2016 8:38 am

plz explain
if x is an integer & (0.5)(.005)(.05)(.005)10^x is an integer, what is the best possible value of x?
A.8 B.9 c.10 D.11 E.13

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Source: Beat The GMAT — Problem Solving | Sat Jan 23, 2016 8:38 am

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by [email protected] » Sat Jan 23, 2016 10:02 am

Hi Noman,

This prompt is meant to ask for the LEAST possible value of X.

To determine the smallest value of X that would make that calculation into an integer, we have to deal with all of those decimals first...

(5)(5)(5)(5) = 625
(.5)(.005)(.05)(.005) = the same number, BUT with 9 decimal places....

.000000625

Since (.000000625)(10^X) is meant to be an integer, X has to be 9 (or greater) to eliminate all of those decimal points.

Final Answer: B

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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