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Recurring decimal....tough one

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Recurring decimal....tough one

by fightthegmat » Thu Sep 03, 2009 8:06 pm
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

I believe the logic is to find the recurring decimals and then pick one which is not a recurring decimal

Could someone explain the method to solve this?
Last edited by fightthegmat on Fri Sep 04, 2009 6:54 pm, edited 1 time in total.
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by 4seasoncentre » Thu Sep 03, 2009 9:28 pm
One strategy is to do long division and hope that one of them eventually stops giving you decimals.

I hope someone else has a faster strategy.
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by fightthegmat » Thu Sep 03, 2009 9:37 pm
Well, you would obviously get a answer to it with long division.

But i hope someone knows a strategy to solve this without consuming much time.
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by tohellandback » Thu Sep 03, 2009 10:16 pm
for these questions:
1) check whether you have 3 or 7 in the denominator
2) see if they cancel out with 3's or 7's in numerator
In case there are big numbers involved, check for bigger prime numbers too. But I am yet to see a question where u need to check for numbers >7


A. 10/189-denominator has 3*7*9. Numerator does not have those numbers. Numerator has 2*5. this will give you non terminating decimal


B. 15/196 - denominator has got 4*7*7. it will give non terminating
C. 16/225 -got 3 in the denominator
D. 25/144 got 3's in the denominator
E. 39/12 - got 3 int he denominator but also got a 3 in the numerator and they will cancel each other-
This is the answer E
The powers of two are bloody impolite!!
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by sanjana » Thu Sep 03, 2009 10:27 pm
The strategy here should be to see if you can get a 4 in the denominator after simplifying the fraction because division by 4 always gives a terminating decimal.

If you see answer choice E

39/12 = (13*3)/(4*3) = 13/4 = 3.25

Hence E.
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by chetanojha » Sat Sep 05, 2009 1:49 pm
I would suggest this link and read Ian Stewart's explaination.
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