carcass wrote:
Is x/y a terminating decimal?
(1) x is a multiple of 2
(2) y is a multiple of 3
I do not know how to evaluate this question. I mean: for me 1 and 2 are insuff because we do not know alternatively of the other variable. Together we do not have the information that we want ok E is the answer
BUT if we have
\frac{4}{9} we know that 9 is not in the form
2^n * 5^m so is not a terminating decimal ok ------->
\frac{18}{24} reduced is
\frac{3}{4} and
neither 4 is in the aforementioned form 
here the OA explanation. may be is late in my TM but I'm confused
Quote:
Statement 1 indicates that x is a multiple of 2, which has nothing to do with
terminating or non-terminating property of decimals. For instance 2/4 is a
terminating decimal while 4/6 is a non terminating decimal. So, NOT SUFFICIENT.
Statement 2 says that y is a multiple of 3, but gives no information about the
common factors of x and y if any, and what is x/y in lowest terms. For instance, 2/3
is non-terminating while 9/12 is terminating. So, NOT SUFFICIENT.
Taking statements 1 and 2 together, 4/9 which satisfies both the statements is non-
terminating, while 18/24 is a terminating decimal. So NOT SUFFICIENT.
The correct answer is E
Actually
4=2^2*5^0, thus
\frac{3}{4}=0.75 is a terminating decimal.
If the denominator has only 2-s and/or 5-s then the fraction always will be a terminating decimal (in this case it also doesn't matter whether the fraction is reduced or not).Is x/y a terminating decimal? (1) x is a multiple of 2. Not sufficient since no info about y.
(2) y is a multiple of 3. Not sufficient since no info about x.
(1)+(2) If
x=2 and
y=3, then
\frac{x}{y}=\frac{2}{3}=0.666... which is NOT a terminating decimal, but if
x=6 and
y=12, then
\frac{x}{y}=0.5 which is a terminating decimal. Not sufficient.
Answer: E.
THEORY:Reduced fraction
\frac{a}{b} (meaning that fraction is already reduced to its lowest term) can be expressed as terminating decimal
if and only b (denominator) is of the form
2^n5^m, where
m and
n are non-negative integers. For example:
\frac{7}{250} is a terminating decimal
0.028, as
250 (denominator) equals to
2*5^3. Fraction
\frac{3}{30} is also a terminating decimal, as
\frac{3}{30}=\frac{1}{10} and denominator
10=2*5.
Note that if denominator already has only 2-s and/or 5-s then it doesn't matter whether the fraction is reduced or not.For example
\frac{x}{2^n5^m}, (where x, n and m are integers) will always be terminating decimal.
(We need reducing in case when we have the prime in denominator other then 2 or 5 to see whether it could be reduced. For example fraction
\frac{6}{15} has 3 as prime in denominator and we need to know if it can be reduced.)
Hope it helps.
I did not know (or notice) the red part albeit I read the theory in the gmatclub math book
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60% (02:04) correct
