A series is given 1,6,7,13,20,33,........and so on.Find the sum of first 52 terms.

a]192847456374
b]243768954321
c]287621088425
d]357849113670

• Ans: 352849113670
  1st and 2nd terms are 1,6
  3rd term is 7 which is sum of first+second.
  4th term is 13 which is sum of second + third.
  Expanding the series further by adding a few more terms, it is
  1, 6, 7, 13, 20, 33, 53, 86, 139 and so on.
  
  Now if we add the terms for upto 1,2,3,4,5,6 terms it is
  1, 7, 14, 27, 47, 80, 133, 219 and so on.
  
  Hence we can infer the sum upto Nth term is (N+2)nd term - 6
  As 1+6+7 is sum upto 3 terms and it is 5th term minus 6= 20-6 = 14
  As 1+6+7+13+20+33+53 is sum upto 7 terms and it is 9th term minus 6 = 139-6 = 133
  
  Hence sum upto 52nd term is nothing but 54th term -6.
  
  Now our task is to find 54th term.
  Using the golden ratio we can easily find the 54th term. But we will just find few more terms for accuracy.
  1, 6, 7, 13, 20, 33, 53, 86, 139, 225, 364, 589, 953, 1542 which is upto 14 terms.
  
  So 54th term = 1542 * (1.6180339)^40 = 352849113676 approx
  Hence sum will be 352849113676-6 = 352849113670
• 9 years agoHelpfull: Yes(15) No(2)
• Can u send me paper of TCS ??
• 9 years agoHelpfull: Yes(14) No(26)
• 1
  6
  7
  13
  20
  33
  53
  86
  139
  225
  364
  589
  953
  1542
  2495
  4037
  6532
  10569
  17101
  27670
  44771
  72441
  117212
  189653
  306865
  496518
  803383
  1299901
  2103284
  3403185
  5506469
  8909654
  14416123
  23325777
  37741900
  61067677
  98809577
  159877254
  258686831
  418564085
  677250916
  1095815001
  1773065917
  2868880918
  4641946835
  7510827753
  12152774588
  19663602341
  31816376929
  51479979270
  83296356199
  134776335469
  
  ANS:352849027131
  
• 9 years agoHelpfull: Yes(3) No(20)
• @swayanti bhaumik ,
  
  You can't predict the answer . Also it may sum upto even number of times , it can't be even as it includes both even and odd numbers in it .
• 9 years agoHelpfull: Yes(2) No(1)
• add last digit only
  we get as last digit as 1
• 9 years agoHelpfull: Yes(2) No(4)
• can anybody explain the ans
• 9 years agoHelpfull: Yes(2) No(0)
• A should be the answer...
  Number should be even and last digit should be non zero
• 9 years agoHelpfull: Yes(1) No(5)
• plz any bdy snd me tcs question,,devirtiwari011@gmail.com
• 9 years agoHelpfull: Yes(0) No(0)
• answer is b
• 9 years agoHelpfull: Yes(0) No(0)
• ananth how will you solve it
• 9 years agoHelpfull: Yes(0) No(0)
• Can u send me paper of TCS ??
  my mail id is priagr@live.in
• 9 years agoHelpfull: Yes(0) No(0)
• how we will find 54th term, so that can obtain sum upto 52th term?
  
• 9 years agoHelpfull: Yes(0) No(0)
• how solve this question??????
  
• 8 years agoHelpfull: Yes(0) No(0)