consider the sequence 1 -2 3 -4 5 -6,... what is the average of the first 200 terms of the sequence?

• Sum of first 10 terms in that series =1-2+3-4+5-6+7-8+9-10=-5
  Sum of 200 terms=20*-5=-100
  Avg=-100/200=-0.5
• 8 years agoHelpfull: Yes(19) No(1)
• 1-2=-1 so the sum in the first two terms =-1
  so for 200 elements it will be -100
  and so the average of first 200 is= -100/200= -0.5
  
• 8 years agoHelpfull: Yes(7) No(0)
• answer is -100
• 8 years agoHelpfull: Yes(4) No(1)
• answer is -0.5
  
• 8 years agoHelpfull: Yes(2) No(4)
• average of first n odd numbers will be n.
  average of first n even numbers will be n+1
  in 200 numers , 100 are odd and 100 are even.
  for 100 odd numbers, average is 100
  for 100 even numbers average is 101.
  therefore , (100-101)/2= -0.5
  
  
• 8 years agoHelpfull: Yes(2) No(0)
• -100 is the answer
• 8 years agoHelpfull: Yes(1) No(6)
• we can do this question by using arithmetic series
  (1+3+5+.....+199) - (2+4+6+.....+200)
  = [ {n1/2}*{(a1+l1)} ] - [ {(n2/2)}*{(a2+l2)}]
  = [ {100/2}*{(1+199)} ] - [ {(100/2)}*{(2+200)}]
  = -100
• 8 years agoHelpfull: Yes(1) No(2)
• @jakki... plzz explain how...??
• 8 years agoHelpfull: Yes(0) No(0)
• Number at even position = -2(n) => -2*1 , __ , -2*2 , __ , and so on
  Number at odd position = odd numbers
• 8 years agoHelpfull: Yes(0) No(1)
• answer is -0.5
• 8 years agoHelpfull: Yes(0) No(0)
• break down it like
  1,3,5,.. + ( -2 )( 1 , 2, 3,...)
  an = a1 + (n-1)d
  you will get
  199 - 200
  = -1
• 8 years agoHelpfull: Yes(0) No(1)
• (1+3+5+..199)-(2+4+6+8....+200)
  t1-t2
  t1=1+3+5+...199
  t2=2+4+6+.....200
  t1=100/2*100(1+199)=100
  t2=100/2*100(2+200)=101
  now;
  100-101=-1
• 8 years agoHelpfull: Yes(0) No(2)
• so much of confusion in this problem
  please give one unique solution
• 8 years agoHelpfull: Yes(0) No(0)
• 1,-2,3,-4,5.-6.
  1-2=-1
  3-4=-1
  5-6=-1
  there are 200 terms so we get 100 1's
  avg for 100 terms =100*(-1)/200=-100/200=-0.5
  
• 8 years agoHelpfull: Yes(0) No(0)
• 1,-2,3,-4,5,-6........200.
  sum=(1+3+5+7...199)-(2+4+6+8+....200)
  =10,000-10,100
  = -100. avg= -100/200
  = -0.5
• 8 years agoHelpfull: Yes(0) No(0)