though may be easy....but not getting[2]
if x_{1}^{2}+x_{2}^{2}+x_{3}^{2}........x_{20}^{2}=400
y_{1}^{2}+y_{2}^{2}+y_{3}^{2}........y_{20}^{2}=900
find
\frac{x_{1}}{y_{1}}+\frac{x_{2}}{y_{2}}+\frac{x_{3}}{y_{3}}+...........\frac{x_{20}}{y_{20}}
1well as for the sorce of the q......this is from mathematics today....tagged under a column challenging.....so possibility is that this q is correct......however since bhaiya is saying this q is wrong ...so i cannot surely say that this q is correct.....
1Agree with Nishant
but I think I have found out the minimum value of the expression (if xi's and yi's are +ve)
so keeping this question alive and a bit of modification from my side find the minimum value with all quantities given positive.
1Lets take i = 1 ,2 ,3, 4,..
and make x1 / y1 = ... = xi / yi
there is a rule in proportions that ,
i a / b = c / d = e / f = ... = x / y = √a2 + c2 + e2 .......√b2 + d2 + f2 + ......
applying that here , x1 / y1 = ... ...... = xi / yi = √x12 + x2 2 + .... / √y12 + ....
= 20 / 30
= 2 / 3
so x1 / y1 + x2 / y2 + ... = 20 x 2 / 3 = 40 / 3
62how did you get to know so much history about me!
when did i say any of this on tiit? [7]
1Nice work Soumya
I was knowing about RMO thing but knew your rank today itself :P. Anyways belated congrats :D
1but dats the same ans dat i gave....
though with another concept.... [7]
13@dukhi... Waise, u don't necessarily need a reason to Smile [1]..
Bhaiyaa even i was thinking tht the no. might not be defined at all...
1nishant sir u never told us all this.....
Class X from St. Joseph’s School, Bhagalpur Class XII from Delhi Public School, RK Puram
Graduation from IIT Kharagpur (Mechanical Engineering)
7th rank in Delhi State in Regional Mathematics Olympiad
99.98 %ile rank in CAT 2008
Deeply Interested in the dynamics of the Stock Markets, is passionate about Mathematics and loves to play badminton.
62wow .. this person seems to be someone heard of... :D [1]
and now i seem to know the source of this info too.. [3]
btw I never sat for the interview so din have the "final call" for bangalore...
And btw that is the list of all the things i seem to have done :P :D
1lolzz sir u are gr8
u even had sumthing to do with ISI(nt the terrorist one) na???
62btw.. did i forget to say that you are are targetiitian and me too
[4]
1ok finally u all think this q is wrong haan........
btw good research haan dukhiatma and arshad......i din knew that[3]
1something is still missing in this research ..... actuarial analysis !!
1m not getting even nearer to d answers.......plz help ne1
1nopes dude [2]
i actually dont know the ans....but that ans of urs is not in teh options
1well knowing teh options wont in any way help u in this q
anyways options r
2/3
3/4
4/9
3/2
1if we consider x1=x2=...=x20=x
and y1=y2=y3......=y20=y
as it is nowhere given in question dat they cant be equal...
so we get x/y=2/3
so 20x/y=40/3
1araay but how u took them as equal.....x1,x2,x3.......they r all different....anyways even with wat u done....ans isnt matching [4]