ISI 2012 ME - I Answer Key

[SoniaKapoor]

Q 22 ...help needed

[manisha]

can some one please explain question no.-3

[Granpa Simpson]

take x>=0, which gives f(x)= x/(1+x), Now differentiate f(x) wrt x it gives f'(x)=[1/(1+x)]-[x/(1+x)^2]=1/(1+x)^2>=0 for all x>0, so the function is monotone increasing for this domain of x hence ans is option a.

[Granpa Simpson]

For Q3, elements of A1 can be derived by putting n=1 and k=1,2,3....in A(n)=(n+1)*k, thus A1={(1+1)*1, (1+1)*2, (1+1)*3,(1+1)*4.......}={2,4,6,8,10,12,14,16,18...}, similarly A2= {3,6,9,12,15,18.......},
Thus A1 intersection A2= {6,12,18,24,........}= A5, verify putting n=5 and respective values of k with A5.

[Granpa Simpson]

for Q23 use integration(logx)= log mod(x), remember its not log x which implies log mod(-4)=log 4 and similarly log mod (-1)= log 1, use this after integrating (1/x) and u will get answer as -log (4), so option d is the answer.

[manisha]

thanku

[neha 1]

pls explain ques 11

[The Villain]

@neha Let sides of rect be x and y resp
area=l*b
=x(l-x)
=lx-x^2
diff wrt x
l-2x=0
x=l/2
second order condn also satisfied
thus line should be divided in 1:1

[neha 1]

thanks ron
pls explain ques 7

[jack]

can someone explain Q.23 and Q.25???

[OSK]

Hi All,

Can some one please help me with :

Q 8 (unable to understand the question part) a link to understand this is much appreciated.

Q 12 (I got the correct answer by random substitution, but please explain the methodology)

Q 18

Q 24

Q 30 (I feel it is C and not A )

[rongmon]

Q 24.

Begin by determining probability that none of the plugs pulled are faulty.

This is : (4 C 2)/ 6 C 2.

We get 6/15.

The probability that atleast one is faulty therefore is simply 1 - (none being faulty).

Thus, 1 - 6/15.

Ans. 9/15



Q 30.

I suspect its C as well, f(x) seems to increase for every value of x.

[shruti malhotra]

can someone  please help me with q:-26

[Dr. Strange]

No. of ways = C(6,3)*C(5,2)  -  C(4,1)*C(5,2)
                  =160

[Saunok]

Can someone please explain the answer to the first question? Why isn't the answer 8?