jnu 2011

[aastha]

Suppose we know that |a|<3. which of the following conditions is enough to imply that |b|< 5 ??
a) |a+b| < 8
b) 2< |a-b| <8
c) |a-b| <= 2
d) 3 < |a-b| < 5

[Ram]

|a+b|<= |a|+|b|  so here |a|<3, |b|<5 for this |a+b|<8.....1st option...

[anon_econ]

I'm getting c.
if a=1 then a) and b) r true even for b=6. if a=2 then d) is true even for b=6. Therefore none of a),b) or d) is implying |b|<5.

[Ram]

yup true answer is C....:)

[ritu]

43.suppose x,y,z be statements.suppose we know that "x is true implies y is true". and "x is false implies z is true".if we know that z is false,then we can conclude that....
a.both x nd y are true..
b.both x nd y are false
c.x is true and y is false
d.x is false nd y is true


44.let x,y,z be statements.suppose we know that x implies y and that y implies z.if we also know that y is false,we can conclude that
a.x is true
b.x is false
c.z is true
d.z is false


45.suppose that one wishes to prove that "if some x are y ,then some z are w".to do this it wud suffice that--
a.some x are z,nd some y are w
b.some z are x ,nd some w are y
c.all x are z ,nd all y are w
d.all z are x,and all w are y


guys pls answer these...nd tell the procedure how to do this....i get very confused in such questions...

[anon_econ]

Hey ritu u need to get ur concepts of logic right for this. Try the chapter on mathematical reasoning from class 11's book.

[ritu]

Hi vasudha...as u recommended i went thru that chapter....nd i feel that answers are optiom a for 43 nd option b for 44...bt i still cant do 45...
Pls tell me whether my answers are wrong nd hw to do 45th
thanx dear:-)

[ritu]

@vasudha
pls see this post:-)

[anon_econ]

Hey. I'm getting the same answers for 43 n 44 :)
For 45, according to me it should be c.
If we know that all x are z, and all y are w, then
if some x are y, then some z are y
and now all y are w would further mean that some z are w.
So if c) is sufficient to prove the given statement.

[Monika]

do u guys hav sis 2011 jnu??..can sum1 plz upload it :/

[arsh]

Hi pls help me with this ques...

if a=2 and b=-2
then |a-b|=4...then how can c) be valid?

[maahi]

 property : |x|-|y|<=|x-y|

mod a-b = mod a -mod b = 2-2 = 0