CBSE maths

1 wrong question of increasing and decreasing functions(where the function itself was not given) assured 6 marks on attempting but still had a long and tiresome test and not a perfect maths test i wud hav wanted.
how was urs?
ans verification needed:a family has 2 children,find the probability that both are boys given that:
1)atleast 1 is a boy
2)the elder one is a boy

34 Answers

1
JOHNCENA IS BACK ·

i did a hell lot of mistakes today....[set-1]

plz tell if i will get any marks for it:::
1.in linear diff. equation i did not take exponent of integrating factor[2]
2.for boy probability one i just wrote answers.....as time was less[2]
3.for other differential i wrote an answer in taking exponent of tan-1 to remove log from other two terms.which we don do usually will they try to understand it or strike off my answer??
4.for cos @ substituion differential two might be possible answers a negative and a positive.i wrote negative one in marking scheme they give only one answer???[2]

11
SANDIPAN CHAKRABORTY ·

@tapan ya... something like this

5 ± ()log ± ()log

cant remember whether + or - ...

1
tapan ·

ya exavtly
igot 5±log(15/8)±log(sumthin)

11
SANDIPAN CHAKRABORTY ·

ya mine one also looks like this only

but that probability question is still a big ?

1
tapan ·

sandipan did u get the answer to area question(are bounded in the interior of 4x2+4y2=9 and the parabola x2=4y)

11
SANDIPAN CHAKRABORTY ·

i did the triangle one..

1
Arka Halder ·

for the area integration got a sin inverse 2√2/3 +sumthing +sumthing
dont remember exactly

1
JOHNCENA IS BACK ·

hey....probabbility 6 mark was easy[but i don want to stop ur grey cells from working so giving a hint:think of all formula u have in syllabus[not mathematical expression but the statement with that formula[1][1]
if anyone finds out ok.else at night i m giving full solution ok??]

BUT IRONY:::::::::::;
i told all students in my room how to do this question.but see wat pity.......in telling them many times i thought i did it......n cam home to see i have left it[2][2].as there was no tick nor do i remember writing in my paper telling them created a feel that i solved it[3][3]........this year is going too unlucky for me[2]

1
Arka Halder ·

what do u mean AISSCE?
where were the invigilators?
and i heard from some who could do that that the ans was 3/5 and application of baye's theorem

1
t2sif ·

anyway thnks arka n sandipan

if anybdy come to no abt it plz do tell me

thnks all

1
JOHNCENA IS BACK ·

@yaar cheating karane me expert hain[1][1]

1
Arka Halder ·

i think a lot will depend on d examiner who gets ur copy[4].
same for me[4].otherwise 0/6 in probability,although i wrote whatever thing was close to the problem[3]

1
JOHNCENA IS BACK ·

no tries???????

answer is 1/4[sorry in hurry wrote wrong [1]]

11
SANDIPAN CHAKRABORTY ·

really... is the answer 1/4...

if the method of the sum is utter rubbish... but answer correct.. how much marks am i supposed to get???

this is what i've done.... plz reply.... got too excited seeing AISSCE's edited post..

P(two balls white)=1/2

P(no balls white)=1/2

P(all balls white)=1/2 x 1/2 = 1/4

i know this has no meaning... can i sttill expect some... some marks !!! [112]

106
Asish Mahapatra ·

I got 3/5 (one of my frnds asked me to solve it)
Similar question also der in ADG... so verified from there

13
Avik ·

Dekho i posted my sol.n here (those who need it)

http://targetiit.com/iit-jee-forum/posts/probability-15330.html

Ppr theek-thak tha, no chance of a 100 [2]...but expecting 96 at least.

1
JOHNCENA IS BACK ·

really asish???[plz tell me the ques no. and pg no.[1]]

1
t2sif ·

any one whu can answr 6 mark prob q on white balls

1
sakshi pandey pandey ·

wat was the ans to that 6 marks probality ques on white balls?
plz reply

1
Arka Halder ·

me too got the same che[1].
hence verified.

1
sakshi pandey pandey ·

QED

1
arsh sharma ·

aisa koi question nahi tha

1
t2sif ·

i gt 3/5

39
Pritish Chakraborty ·

I've lost 7 marks till now..lols. Did any of you get that question in which three points were given, we had to find their vectors and also find the fourth point(they were part of a parallelogram)? I tried coplanarity but the lambda parameter vanished on using it! haha. So I had to do it using cross product of vectors(area of ||gm).

1
t2sif ·

bt i m nt sure ????/

wt did u gt n how?????

1
t2sif ·

any one whu can answr 6 mark prob q

1
Che ·

1) 1/3

2) 1/2

1
Arka Halder ·

no pritish had no such ques.
cud do all ques on vectors and 3D amazingly!probability and 1 long integration almost took my soul out of me[2]

1
t2sif ·

guys plzz tell

1
Arka Halder ·

sorry t2sif cudnt do that 1.
hrd from friends that the ans is 3/5 as u said.

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