In (1) (2 3) (4 5 6) (7 8 9 10). Find out the sum of terms in 50th bracket.can any one explian it

1) 62525
2) 37525
3) 7875
4) none of the above

• 62525
  
  up to 49 brackets, number of numbers covered will be
  1+2+3+...+49= 49*50/2= 1225
  
  50th bracket will have numbers 1226,1227,.......1275 (50 numbers)
  
  sum of these 50 numbers will be (50/2)*(1226+1275)= 26*2501=62525
• 11 years agoHelpfull: Yes(2) No(0)
• We take the 1st term of every bracket i.e. 1,2,4,7,11,16,.....
  We can generalize this series as [{n(n-1)/2}+1]=(n^2-n+2)/2
  So, we can find the 1st term of 50th bracket as (50^2-50+2)/2 = 1226
  So we may write 50th bracket as (1226 1227 1228 1229 . . .)
  Its an A.P. sum of terms in 50th bracket = (50/2)[{2*1226)+(50-1)*1]
  = 25*2501=62525.Ans
• 11 years agoHelpfull: Yes(0) No(0)
• This follows Sigma n series, In 4th bracket Last term 10 = 4*5/2 therefore in 50th bracket the last term will be 50*51/2 = 1275.
  We have to add previous 49 terms with 1275 (There will be 50 terms in 50th bracket)
  Then Answer is 62525
• 9 years agoHelpfull: Yes(0) No(0)