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Terminating decimals

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Terminating decimals

by rakeshd347 » Wed Oct 16, 2013 3:12 am
Hi Everyone,

I have this question today in gmatprep test and I was kind of confused and I did educate guessing. I have seen quite a few questions in the recent past on this topic can some one suggest me what to do in these cases.

The questions generally ask which of the following not yield or will yield a terminating decimal.

4/128
23/45
48/198

Now I have made these numbers myself but these question I have seen quite a few. I know anything divided by 3 or 9 or 11 will give non terminating and anything divided by 2 or 5 will give terminating decimal. But is there a rule or list which I can refer.
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by GMATGuruNY » Wed Oct 16, 2013 3:55 am
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by Brent@GMATPrepNow » Wed Oct 16, 2013 6:57 am
rakeshd347 wrote:Hi Everyone,

I have this question today in gmatprep test and I was kind of confused and I did educate guessing. I have seen quite a few questions in the recent past on this topic can some one suggest me what to do in these cases.

The questions generally ask which of the following not yield or will yield a terminating decimal.

4/128
23/45
48/198

Now I have made these numbers myself but these question I have seen quite a few. I know anything divided by 3 or 9 or 11 will give non terminating and anything divided by 2 or 5 will give terminating decimal. But is there a rule or list which I can refer.
There's a nice rule that says something like,
If a/b results in a terminating decimal, then the denominator, b, MUST be the product of 2's and 5's only!
So, for example, if b = 20, the fraction a/b will result in a terminating decimal. The same holds true for other values of b such as 4, 5, 25, 40, 2, 8, and so on.
If b is NOT the product of 2's and 5's only, then a/b will NOT be a terminating decimal.

NOTE: the above rule assumes that a/b is written in simplest terms.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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