GATE Question of the Day - General Aptitude Question

Examsavvy
15


The sum of n terms of the series 4+44+444+------ is


Please give the reason for your answer. All the best

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15 Comments

  1. option C....just take 4 as common and take the g.p of the terms ... we will get the answer..

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  2. It's C
    Its just as easy as substituting value of 'n' and checking options.

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  3. yaaa checking is easy... bt we can do it through process also

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  4. ya from my knowledge answer is "c"! but i have doubt on this?

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  5. yah it is C because it is in the geometric progression

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  6. hey after a stong confirmation i found the right answer the same option "C"

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  7. option c......
    simple trick is that put only n=o,then we see that all term become zero.which only in case option c.so don't waste your time use short trick.

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  8. yaa... put n=o.. den only in c ol terms wil be zero... so ans. is "C"

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  9. Answer to this question is option C

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  10. this question is very easy.put n=1 then u will get the 4...so option c

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  11. sum= 4+44+444+.........+tn
    sum= 4+ 44+.........+tn-1+tn

    subtracting above two equations we get

    0=4+40+400+.............+(tn-tn-1)-tn
    tn=(4+40+400+...n terms)
    tn=4*(10^(n)-1)/(10-1) -- G.P summation
    sum=sigma of tn
    sum=4/9*(sigma of 10^(n)-sigma of 1)
    sum=4/9*[10*(10^(n)-1)/(10-1)-n]
    sum=option 'C'

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