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Concentration: General Management, International Business

GPA: 3.65

Re: If a, b, c and d are positive integers, is d odd? [#permalink]

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29 Sep 2016, 14:04

2

This post received KUDOS

msk0657: Stat 1: a/b = 2c...here 2c will always be even...i.e. a and b have to be even...even / even will yield even

>> Not necessarily 12/3 = 4, we just know from this statement that a is even, but we dont know if b is even or not ...

Second statement does not give any new information as well ... a/c = d+1

IMHO, combining statement 1 and 2 also does not tell anything about d from 1 we know that a is even, so combining 1& 2 if c is even then d is even if c is odd then is odd ...can't conclude...Hence E for me.

This is a DS Yes\No question asking whether d is odd. Answering a definite "Yes" or a definite "No", i.e., answering "d is odd" or "d is even" means Sufficient. If the answer is sometimes "Yes" and sometimes "No", i.e., "d can be either odd or even", it means Maybe which means Insufficient.

Stat.(1) tells you nothing about d and therefore cannot, on its own, be sufficient. d could be either odd or even. Hence, Stat.(1)->Maybe->IS->BCE.

Stat.(2): plug in \(a=2\), \(c=1\), so \([m]2/1\)=d+1[/m], or \(d=1\), which is odd. Plug in \(a=3\), \(c=1\), so \(\frac{3}{1}=d+1\), or d=2, which is even. d could be either odd or even, so Stat.(2)->Maybe->IS->CE.

Stat.(1+2): manipulate the variables in both equations to get

\(a=2bc\) and \(a=c(d+1)\)

--> \(2bc=c(d+1)\).

Divide by c to get:

--> \(2b=d+1\), which can also be represented as \(even=d+odd\). d, therefore, must also be odd, so Stat.(1+2)->Yes->S->C.
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Concentration: General Management, General Management

Re: If a, b, c and d are positive integers, is d odd? [#permalink]

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07 Mar 2017, 00:46

S1: a/b=2c

No information is provided about d here. So this statement is not sufficient.

S2: a/c=d+1

Whether d is odd or even will depend on the values of a & c. But no information about values of a and c has been provided here.So this statement is not sufficient.

Combining both S1 & S2:

From S1 we have a=b*2c. Substituting this value in S2 we get

\frac{(b*2c)}{c=d+1} On simplifying we have 2b=d+1 ie. d= 2b-1

now 2b is even so 2b-1 will be odd. Hence d is odd. So both S1 & S2 are sufficient together.

Re: If a, b, c and d are positive integers, is d odd? [#permalink]

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24 Aug 2017, 23:18

Statement 1 : (a/b) = 2c

c can be odd or even, but 2c will always be even. Hence (a/b) will be even. So (a/b) can be (even/even) or (even/odd) -> Eg (6/3) In both cases, a has to be even but b can be even or odd.

Statement 2 : (a/c) = d+1

From Statement 1 we know a is even for sure. We also know that (even/even) or (even/odd) leads to even number. So d+1 will be even. Hence d has to be odd number.

Please give kudos to the answer if I could help you understand