Manhattan test 3 - DS doubt

[shivani.magan]

Is the product st negative?

(1) s2 - s < 0
(2) s-4/t-3 = 1


A.Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B.Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C.Both statements TOGETHER are sufficient, but NEITHER one ALONE is sufficient.
D.EACH statement ALONE is sufficient.
E.Statements (1) and (2) TOGETHER are NOT sufficient.

[killer1387]

Is the product st negative?

(1) s2 - s < 0
(2) s-4/t-3 = 1

1. 0<s<1, insuff
2. s=t+1 (assuming the written relation is (s-4)/(t-3), do use brackets to remove ambiguity)
insuff.
1 & 2
-1<t<0
hence sufficienct

thus C

[nakul.maheshwari]

Wait a minute..is it (s-4)/(t-3) = 1 or s-(4/t)-3 = 1;

If it is (s-4)/(t-3), shouldnt the answer be B?

s-4 = t - 3
s-t = 1

If s = +ve, then t = +ve
If s = -ve, then t = -ve
S and t cannot have opposite values, hence s.t is never negative.

Answer B? what am i missing here?

[nakul.maheshwari]

Never mind, just realized that 't' can be "0" also

[ranjeet75]

I think E should be the answer.

Stat 1: S(s - 1) < 0
so, either s < 0 or s < 1

Insuff as we don't know abt t

Stst 2: s - 4 = t - 3

s = 1+t but s and t both can be either +ve or -ve.

Both: s = 0.9 so, t = - 0.1, so st = -ve
s = 4 so, t = 3, st = +ve

[shivani.magan]

I think E should be the answer.

Stat 1: S(s - 1) < 0
so, either s < 0 or s < 1

Insuff as we don't know abt t

Stst 2: s - 4 = t - 3

s = 1+t but s and t both can be either +ve or -ve.

Both: s = 0.9 so, t = - 0.1, so st = -ve
s = 4 so, t = 3, st = +ve

but s cannot be 4 because s<0 or s<1
however s can be negative . if s - -2 then since s= t+1 t = -1 and st becomes positive. what i am doing wron here?

[shivani.magan]

Is the product st negative?

(1) s2 - s < 0
(2) s-4/t-3 = 1

1. 0<s<1, insuff
2. s=t+1 (assuming the written relation is (s-4)/(t-3), do use brackets to remove ambiguity)
insuff.
1 & 2
-1<t<0
hence sufficienct

thus C

Can u see above and tell me what am i doing wrong here?

[killer1387]

but s cannot be 4 because s<0 or s<1
however s can be negative . if s - -2 then since s= t+1 t = -1 and st becomes positive. what i am doing wron here?

Is the product st negative?

(1) s2 - s < 0
(2) s-4/t-3 = 1

The part in bold is wrong
from
(1)s2 - s < 0
0<s<1
so s is positive.--> insufficient

(2) s=t+1
insufficient
from 1 & 2

s is positive
and
0<t+1<1
i.e. -1<t<0
i.e. t is negative

hence st is negative
sufficient.
so C

Hope this clarifies.

[killer1387]

Wait a minute..is it (s-4)/(t-3) = 1 or s-(4/t)-3 = 1;

If it is (s-4)/(t-3), shouldnt the answer be B?

s-4 = t - 3
s-t = 1

If s = +ve, then t = +ve
If s = -ve, then t = -ve
S and t cannot have opposite values, hence s.t is never negative.

Answer B? what am i missing here?

the part in bold is wrong.
(2)
t=s-1
If s = +ve, then t = can be both +ve and -ve
i.e. for 0<s<1 => t<0
for 1<s<infinity => t>0
so insufficient

HTH

[teal]

Stat 2 says s = t+1; There are three possibilities a) one of them can be zero and the other either positive or negative; b) both can positive c) both can be negative

In either of these three cases product st will be either positive or zero so the answer will be NO

Wouldn't that mean B as the answer? Can someone please give me a case when product st will be negative given the conditions of statement (2).