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Intern
Joined: 11 Oct 2009
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Rules for Odd and even number operations
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14 Dec 2009, 12:35
Hi all,
I was just reviewing the rules for odd and even number operations:
Odd + Odd = Even Even + Even = Even Odd +Even = Odd
Odd x Odd = Odd Even x Even = even Odd x even = even
(Essentially the only things that result in odd numbers are: odd + even = Odd and Odd x Odd = Odd)
And was wondering if anyone could confirm  do these rules also apply to subtraction and division?
Ie) odd  even = odd or even  odd = odd and Odd divided by odd = odd
Off the top of my head, they seem to work for division and subtraction as well.



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Re: Rules for Odd and even number operations
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15 Dec 2009, 22:34
Yes, it works for subtraction, but not division. Division can result in noninteger answers so beware of division!
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Rules for Odd and even number operations
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16 Jun 2015, 23:42
Is there any rule for division?
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Re: Rules for Odd and even number operations
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17 Jun 2015, 01:04
Subanta wrote: Is there any rule for division? As mentioned in the post above yours, division is tricky. For example, 9/3 = integer but 5/3= 1.67, not an integer. 2/4= not an integer but 6/2 or 4/2= an integer. Thus, odd/odd may or may be not an integer. Similarly, even/even may or may not be an integer. The best way out is to test a couple of simple cases as shown above to tackle DS problems that deal with such equations.



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Re: Rules for Odd and even number operations
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15 Jul 2015, 10:16
Engr2012 wrote: Subanta wrote: Is there any rule for division? As mentioned in the post above yours, division is tricky. For example, 9/3 = integer but 5/3= 1.67, not an integer. 2/4= not an integer but 6/2 or 4/2= an integer. Thus, odd/odd may or may be not an integer. Similarly, even/even may or may not be an integer. The best way out is to test a couple of simple cases as shown above to tackle DS problems that deal with such equations. Thank You Engr2012
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Rules for Odd and even number operations
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15 Jul 2015, 10:38
ael719 wrote: Yes, it works for subtraction, but not division.
Division can result in noninteger answers so beware of division! since even number can be written as even * odd or even * even so even / even can be even * even / even which is even even * odd / even can be odd. So even / even can be both odd and even. Similarly even / odd can be even .



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Re: Rules for Odd and even number operations
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15 Jul 2015, 19:44
Hi abhinav008, You have to be careful about your Number Property rules; from what you've posted, you don't appear to account for NONINTEGER possibilities. For example...Even/Even COULD be even OR odd OR noninteger... eg. 8/2 = 4 8/8 = 1 8/6 = Noninteger Number Property knowledge can be quite useful on Test Day, but if you're going to take a 'theory'based approach, then you have to make sure that you haven't missed any of the possibilities. GMAT assassins aren't born, they're made, Rich
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Re: Rules for Odd and even number operations
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18 Jul 2015, 23:06
Hi,
another 2 (obvious) rules that derive from your own, but still need to be written (for the quick answer):
1. powers don't change the OddEven. what works for me is just "covering" the powers and continue as usual.
2. when i see then term "ax" (while a is a random integer), if a=> even, then i cover the "x" (ax is even) if a=> odd, then i cover the "a" (the even odd property of "ax" is determent solely by "x")
one more point to notice while dividing is that its a derivative of multiplication.
assuming the the multiplication is integer, the only rule is :
ODD X odd = odd(r) => odd(R)/odd = ODD or odd(r)/ODD = odd
because multiply even by any number result an even, the division of even by any number is not clear for its oddeven property.



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Re: Rules for Odd and even number operations
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03 Sep 2018, 15:02
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Re: Rules for Odd and even number operations &nbs
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