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  • The least value of n for which the sum of series 5 8 11 ---- n terms is not less than 670 is
    a 20
    b 19
    c 22
    d 18

    The sum of the numbers from 1 to 100 which are not divisble by 3 and 5 is
    a 2946
    b 2732
    c 2632
    d 2317

    If all the 6's are eplaced by 9's then the algebric sum of all the numbers from 1 to 100 <both Inclusive > varies by
    a 330
    b 333
    c 219
    d 279
    Asked by  2 years ago
     
 
 

Answers (1)

 
  • By , 2 years ago
    Sum = 5 + 8 + 11 + ..... + (5+(n-1)3)
           = (n/2)(10 + (n-1)3) > 670

    => 3n2 + 7n > 1340

    => (n - 20)(3n + 67) > 0

    => n > 20     Option (a)
 
 
 
 

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