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Manager
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decimal equivalent [#permalink]
 09 Jul 2009, 10:29
Question Stats:
0% (00:00) correct
100% (00:46) wrong based on 0 sessions
Which of the following fractions has a decimal equivalent that is a terminating decimal?
A. 10/189
B. 15/196
C. 16/225
D. 25/144
E. 39/128
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Current Student
Joined: 03 Aug 2006
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Re: decimal equivalent [#permalink]
09 Jul 2009, 10:56
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The answer is E.
For a fraction to be a terminating decimal the denominator can contain only the prime factors 2 and/or 5 i.e. the denominator should be in the form 2^a5^b
Looking at each denominator.
A. 189 has the prime factor 3 so the fraction is not a terminating decimal.
B. 196 has the prime factor 7 so the fraction is not a terminating decimal.
C. 225 has the prime factor 3 so the fraction is not a terminating decimal.
D. 144 has the prime factor 3 so the fraction is not a terminating decimal.
E. 128 has the prime factor 2 only and can be written in the form 2^75^0 which makes the fraction a terminating decimal.
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Re: decimal equivalent [#permalink]
09 Jul 2009, 10:58
Thanks a lot.
Nice explanation.
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Re: decimal equivalent [#permalink]
09 Jul 2009, 11:28
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One important point: you should look at numerator as well, as it can simplify denominator. For example, 18/225 is a terminating decimal: 18/225=\frac{3*3*2}{3*3*5*5}=\frac{2}{5*5}.
However, this problem doesn't try to trick you this way.
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Re: decimal equivalent
[#permalink]
09 Jul 2009, 11:28
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