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This question from DS which I instantly solved during the exam, almost every insti's answer key says my answr is wrong :( that we need both statements. i dont see anything wrong with my understanding of the question ... or have i interpreted something wrongly ??
Ok this is the question ....
A family has only one kid. The father says "after n yrs my age will be 4 times my kid". Mother says "after n yrs my age will be 3 times my kid". What will be the COMBINED ages of the parents after n yrs?
A) The age diff between the parents is 10 years
B) After n yrs, the kid gonna be twice as old as she is now.
My take
---------
Let father = F
mother = M
kid = K
Given:
F+n = 4(K+n) ..... (1)
M+n = 3(K+n) ..... (2)
clearly F > M.
Statement A
--------------
F - M = 10
(1)-(2) => F - M = K+n
=> K + n = 10
=> F + n = 40
and M + n = 30
adding, F + M + 2n = 70 .... ANSWER.
Statement B
--------------
=> K = n (currently)
=> F = 7n
and M = 5n
we need F + M + 2n
which we cannot determine from this statement alone.
So answer is (1) (using A alone but not B).
why the hell do we need both of 'em?
--Gaurav
... your simplicity long ended, when you took Persian mistresses and children, and thickened your holdings with plunder and jewels... you have fallen in love with all things in life that destroy men...
Gaurav that is the exact solution I had in mind. Even I checked out various answer keys but all of them had 4 as the answer. So I thought I might have missed something but could not figure it out!! Now I have some1 for company
Re: DS question from CAT 2003 -
17-02-2004, 06:42 PM
Quote:
Originally Posted by poltergeist
Quote:
Statement A
--------------
F - M = 10
(1)-(2) => F - M = K+n
=> K + n = 10
=> F + n = 40
and M + n = 30
adding, F + M + 2n = 70 .... ANSWER.
adding these three, don' u get F + M + 3n = 70 ??
then don't u need the second statement?
regards,
rakesh
no rakesh ... i am adding ONLY 2 eqns ...
F + n = 40
M + n = 30
--Gaurav
... your simplicity long ended, when you took Persian mistresses and children, and thickened your holdings with plunder and jewels... you have fallen in love with all things in life that destroy men...
same thing here.
there is a better chance for clearing di cutoffs if this turns out to be correct.
time has got a different soln. tho, (3)
they do it using (a) alone in a similr fashion
they also compute using b alone. but i cudnt make anything out of it.
their soln is like this
[quote]
Let the present age of father is ‘f’ years
the present age of mother is ‘m’ years and
the present age of son is ‘s’ years.
It is given that (f + n) = 4(s + n) ……… (1)
(m + n) = 3(s + n) ……. (2)
(1) – (2) Þ f – m = s + n ……………. (3)
(1) + (2) Þ f + m + 2n = 7s + 7n = 7(s + n) ……. (4)
From statement A, it is given that
(f – m) or (n – s) = 10.
Substituting in (3), we get s + n = 10.
\The combined age of parents
= 7(s + x) = 7 x 10 = 70 years
\Statement A alone is sufficient.
From B, it is given that (s + n) = 2s => n = s ……… (5)
Substituting (5) in (3), we get s = 5.
Substituting s = 5 in (4), we get
f + m = 14n – 2n Þ f + m = 12n (but n = s = 5)
We can clearly see that, we can get the sum of the ages of father and mother in terms of ‘n’. Since ‘n’ is already defined in the question statement, B alone is sufficient. Choice (3)
[\quote]
the answer 1 is corect.
check out the detailed solutions of CL...
time has made the mistake of using the first statement in the second statement so it is wrong.
"dikhawe pe na jao, apni akal lagao"
sulabh
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