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is OA correct?

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is OA correct?

by magical cook » Thu Dec 13, 2007 11:41 pm
If r, s, and t are positive integers, is r + s + t even?
(1) r + s is even.
(2) s + t is even.

[spoiler]I think C but OA is E - could anyone confirm? [/spoiler]
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by sujaysolanki » Thu Dec 13, 2007 11:47 pm
Try r = 1 s = 3 and t = 1

Conditions one and two hold but r+ s+ t = 0dd Hence E seems correct
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by magical cook » Fri Dec 14, 2007 6:06 am
yeah that's right... :oops:
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by camitava » Fri Dec 14, 2007 7:21 am
Wohhhhhh sujaysolanki! What a catch man... Really appreciable. :)
Correct me If I am wrong


Regards,

Amitava
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by Auzbee » Tue Dec 25, 2007 7:05 pm
If r, s, and t are positive integers, is r + s + t even?
(1) r + s is even.
(2) s + t is even.
1. For r+s= even we have two conditions:
Even + Even = Even
Odd + Odd = Even

Since we don't know about t, it is INSUFF.

2. The above logic holds for condition 2 as well since we don't know about r.

Combine:
We have r+s=Even and s+t=Even. From the logic described in condition 1 - r, s, t should be of the same sign.
Hence
Even+Even+Even=Even
Odd+Odd+Odd=Odd

INSUFF.
Hence E is the right answer.
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