mayankdevnani
Solve this ONE :-
Q-) Problem on SERIES.
6,20,36,48,50,?,0
a)36
b)40
c)46
d)56
Which number comes in place of "?" ?
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mayankdevnani
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@ash2326 @phi @UsukiDoll
mayankdevnani
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how?
UsukiDoll
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Ned Flanders
mayankdevnani
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what?
mayankdevnani
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@INeedHelpPlease? help me
RadEn
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Tn = 7n^2 - n^3
T1 = 7(1)^2 - (1)^3 = 6
T2 = 7(2)^2 - (2)^3 = 20
....
...
T6 = 7(6)^2 - (6)^3 = 78
T7 = 7(7)^2 - (7)^3 = 0
so, it is T6 = 78
mayankdevnani
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but it is not in options. @RadEn
mayankdevnani
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i know this is also a answer but i need answer which is in options?
mayankdevnani
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@hartnn can you help me ?
hartnn
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how did u get Tn RadEn ?
SithsAndGiggles
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@RadEn's reasoning checks out, his answer should be 36 though. \(7(6^2)-6^3=252-216=36\)
mayankdevnani
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he makes the series to solve it. @hartnn
hartnn
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yeah,
i know how to find Tn,
but i wanted to know whether RadEn used any different/simpler method....
mayankdevnani
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his method is wrong.
hartnn
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he got the answer which is in the choices, how u say its wrong ?
mayankdevnani
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because if we put n=6,the answer comes to be is 36 but in actual(followed by series)the answer would be 50
mayankdevnani
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isiliye mujhe lagta h ki voh galat h
hartnn
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" in actual(followed by series)the answer would be 50"
what does this even mean ?
mayankdevnani
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iska matla agar hum uske tarike se follow karien to iska answer 50 aana chaihye series ke hisaab se lekin actual main 36 aa raha h.....
iska method thode se hi digits ke liye apply hota h
mayankdevnani
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now understood @hartnn bhaiya
hartnn
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lol, i could translate that in hindi myself too
hartnn
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why u say answer should be 50 ?
mayankdevnani
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bhaiya , yeh question ntse 2013 RAJ. main poocha gaya tha aur FIITJEE vaalein bata rahein h ki iska answer DATA INADEQUATE h aur CAREER POINT vallein bata rahein h ki iska answer 36 h
mayankdevnani
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to iska kya answer hoga bhaiya?
mayankdevnani
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@hartnn
hartnn
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the answer to this is indeed 36
as shown corretly by RadEn
mayankdevnani
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okk...thank you,,, @hartnn and @RadEn
hartnn
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i just wanted to know any simpler way of finding Tn :P
mayankdevnani
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yeah...this logic doesn't apply in NTSE STAGE 1
mayankdevnani
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i think there is another logic simpler logic for this
hartnn
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i think it does apply,
the third differences are constant
hartnn
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|dw:1385197162928:dw|
hartnn
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so, x - 52 - (-10) = -6
hartnn
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x= 42 - 6 = 36
hartnn
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@mayankdevnani
@RadEn any simpler way to find Tn ?
RadEn
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wolfram is simpler way , @hartnn
hehehe :)
why i cant see notification in OS ??
hartnn
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oh lol
but i guess they can't use wolf....
so using the 3rd difference is a simpler manual way...
RadEn
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yeah, just input some numbers in wolfram :)
hartnn
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and nobody can see notifications
its the bug OS admins are trying to fix
RadEn
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ohhhh, thanks