JNU !

[a.m]

1. If E(X^2) = 16 and var(X)= 4, then E[(2+3X)^2] is approximately equal to :

a. 123
b. 156
c. 143
d. 150
e. none of the above.

guys, my answer comes out to be none of these. If only you could confirm !! Thanks.



2.Suppose a market demand curve of an individual is given by q=100-p. The prevailing price is 50.The supplier of the units is a monopolist and wants to perform first degree price discrimination. He will then :

a. charge a price of 50 for all units
b. charge a price of 60 for the first 25 units and price if 50 for the rest
c. charge a price of 1250 per unit
d. set up a two part tariff in pricing and charge the consumer a flat fee of 1250 and price of 50 per unit
e. set up a two part tariff in pricing and charge the consumer a flat fee of 1250 and a price of 60 per unit.

3. Let f(x)= logx/x where 0<x<1. Then for all x such that 0<x<1

a. f'(x) < 0
b f'(x) >0
c. f'(x)>0, if 0<x<0.5 and f'(x) < 0, if 0.5 <= x <1

[sara]

ans-2       a)

[a.m]

Hi sara. Could you please give me a logic. 1st degree discrimination means selling a product to different consumers at different prices, right ?
How did you arrive at the answer ?

[sara]

i think so,q=100-p,p=50,both are fixed so at a particular quantity level price is fixed.

[sara]

i think so,q=100-p,p=50,both are fixed so at a particular quantity level price is fixed.more over demand curve of individual is given.

[aastha]

q 1 : none of these . .

q2 : f'(x) > 0

[sweta]

HI A.M
Can u tell me how did u get the ans for q1?

[a.m]

@ Sweta :

We know that var(X) = E(X)^2 - [E(X)]^2
putting the values we get,  4 = 16 - [E(X)]^2
and thus, [E(X)]^2= 16-4 = 12
and E(X)= sqrt 12 = 2*sqr root3

now var(2+3X)= 9* var(x) = 9*4 = 36
and E(2+3X) = 2+3 E(X) = 2+  3*2*sqrt 3
and thus [E(X)]^2 = 4+108+41.52 = 153. 53

and now v(2+3X) = 36
E(2+3X)^2- [E(2+3X)]^2 = 36
E(2+3x)^2 = 36 + 153.52 = 189.52


thus, none of the above. Hope you get it now.

[sweta]

@ A.M.

 thanks!

[a.m]

@ Sweta : You're welcome !

[Abu]

Q 3 - a

[faizy]

@ abu...........i think ans. will be< b.>......because logx will be neg. in that interval