Even

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Even

by beater » Fri Oct 10, 2008 6:54 am
If r, s, and t are positive integers, is r + s + t even?

(1) r + s is even.
(2) s + t is even.
Source: — Data Sufficiency |

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by raju232007 » Fri Oct 10, 2008 8:18 am
The ans is E

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by beater » Fri Oct 10, 2008 8:28 am
Could you please explain your reasoning

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by raju232007 » Fri Oct 10, 2008 8:43 am
statement 1:

r+s is even

we know that for the result to be even either both the numbers should be even or both the numbers should be odd
so r&s are both even or r&s are both odd
And moreover we have no info about t

Insufficient

statement 2:

s+t is even

As per the same logic either s &t are both even or s& t are both odd
There is no info about t

Insufficient

Combining both the statements we get

r,s and t are all even or r,s,t are all odd
when r,s & t are all even r+s+t results in an even number
when r,s & t are all odd r+s+t results in an odd number

So the ans is E..

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by vivek.kapoor83 » Fri Oct 10, 2008 9:05 am
E. OA pls

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by beater » Fri Oct 10, 2008 9:42 am
OA - E.

Thanks for the explanation raju232007. I messed up when I combined both the equations and your explanation helped me understand my error.