yogirb8801 wrote:

If for integers a, b, c, and d, a + b + c + d = 4, does d = 1?

(1) abc = 1

(2) ad = 1

Given :- a+b+c+d = 4

asking:- is d = 1??

AD/BCE

statement 1:- abc = 1

Two cases are possible

a=1,b=1,c=1 then d = 1 YES

a=-1,b=-1,c=1 then d= 5 NO

So A alone is not sufficient . AD are ousted.

statement2:- ad = 1

Two cases are possible

a = 1,d = 1 YES

a = -1,d=-1 NO.

so B alone is not sufficient B is ousted

Combine both the statements.

We will get only one case possible which satisfies all the three conditions.

How??

ad = 1 implies two cases a=-1,b=-1 or a=1,b=1

if a=-1 and d = -1 then apply the first condition. then b,c will have -1 and 1 It doesnot satisfy a + b+c+d = 4;

if a=1 and d = 1 then apply second condition then b,c will have 1 ,1 .It satisfies a+b+c+d = 4.So d = 1. YES

SO the answer is C

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