Let's use the method of replacement (assumption) here.
r(2) + s(4) = 6
s(4) + t(8) = 12
So, r+s+t = 2+4+8 = 14
However, because r,s,t are postive integers, the value of any of these letters can be even or odd.
so if we replace the value of t as odd, then
s(4) + t(9) = 13
hence (s+t) + r = 13 + 2 = 15
Hence, the answer is E.
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r + s + t even?
Source: Beat The GMAT — Data Sufficiency |
Each statement by itself is insufficient.
Stmt I
Take r,s to be both even
r+s+t is even if t is even or odd if t is odd
INSUFF
Stmt II
Take s,t to be both even
r+s+t is even if r is even or odd if r is odd
INSUFF
Together r,s,t can all be odd or can all be even satisfying stmt I and II which would make r+s+t odd or even.
Hence E
Stmt I
Take r,s to be both even
r+s+t is even if t is even or odd if t is odd
INSUFF
Stmt II
Take s,t to be both even
r+s+t is even if r is even or odd if r is odd
INSUFF
Together r,s,t can all be odd or can all be even satisfying stmt I and II which would make r+s+t odd or even.
Hence E
Last edited by cramya on Mon Feb 09, 2009 5:22 pm, edited 1 time in total.
THe question asked for is "Is r + s + t even? "
This can be answer if we know whether r,s and t are even / odd.
From stmt 1,
It is given that r + s is even ==> Both r and s should either be even or odd.
No informaiton related to t is given. So if t is even then the sum will be even. And if t is odd, then sum will be odd. Hence insufficient.
From stmt 2 -
It is given that s + t is even ==> Both s and t should either be even or odd.
No informaiton related to r is given. So if r is even then the sum will be even. And if r is odd, then sum will be odd. Hence insufficient.
Now combine both the clues.
r + s is even and s + t is even ==> We can derive that r,s,t are either all even or all odd. So their sum can be either be even or odd. Insifficient.
IMO E
This can be answer if we know whether r,s and t are even / odd.
From stmt 1,
It is given that r + s is even ==> Both r and s should either be even or odd.
No informaiton related to t is given. So if t is even then the sum will be even. And if t is odd, then sum will be odd. Hence insufficient.
From stmt 2 -
It is given that s + t is even ==> Both s and t should either be even or odd.
No informaiton related to r is given. So if r is even then the sum will be even. And if r is odd, then sum will be odd. Hence insufficient.
Now combine both the clues.
r + s is even and s + t is even ==> We can derive that r,s,t are either all even or all odd. So their sum can be either be even or odd. Insifficient.
IMO E
(E)
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GMATPowerPrep Test2= 760
Kaplan Diagnostic Test= 700
Kaplan Test1=600
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Kalplan Test3=570
