1-2+3-.................-100 find the value

• 1-2+3-4.....+99-100 ,this is the sequence
  now, we divide the series into 2 groups..
  
  (1+3+5+7...+99)-(2+4+6+8...+100)
  using A.P sum formula,
  (1+3+5...+99)=50/2(1+99) [s(n)=n/2(a+l)]
  =2500
  again for another sequence
  (2+4+6...+100)=50/2(2+100)
  =2550
  the original sequence was=(1+3+5+7...+99)-(2+4+6...+100)
  = 2500-2550
  = -50 (ans).
• 11 years agoHelpfull: Yes(22) No(0)
• 1-2=-1
  3-4=-1..... similarly -1-1.....50times=-50
• 11 years agoHelpfull: Yes(9) No(1)
• divide the sequence into 2 groups
  sum of odd numbers =n*n (n=number of odd numbers)=2500
  sum of even numbers =(n+1)*n (n=number of even numbers)=2550
  ans is 2500-2550=-50
• 10 years agoHelpfull: Yes(2) No(0)
• it will be-50
  
• 11 years agoHelpfull: Yes(1) No(0)
• -50
• 11 years agoHelpfull: Yes(1) No(0)
• -50 ans...
• 11 years agoHelpfull: Yes(0) No(0)
• ans=-50
  ...50*(-1)
• 11 years agoHelpfull: Yes(0) No(0)