If s and t are positive integers, is s + t even?

Question

If s and t are positive integers, is s + t even?
 
(1) 5s – 1 is even
(2) st is even

Abhishek009 · Answer

FROM STATEMENT - I    ( INSUFFICIENT )  
 
Since, 5s - 1 = EVEN; s must be ODD

Since we do not know the value of t we can not find the value of s + t

FROM STATEMENT - II   ( INSUFFICIENT )

Either s /t is EVEN or Both s & t are even

FROM STATEMENT - I & II   ( SUFFICIENT )

Since from statement I we know s is even and combining statement II , we get t = EVEN

Thus, s + t will be EVEN

Hence, BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked, answer will be (C)

yezz · Answer

FOR S+T TO BE EVEN both has to be odd or both has to be even

from 1

s is ODD and no info about t ... insuff

from 2

one of them is even .. INSUFF

BOTH
 one odd and the other is even then their summation must be odd.. suff

c

If s and t are positive integers, is s + t even?

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