find the value of 21+22+.....+60,if 1+2+....+40=820

• 1620
  
  21+22+23+....+60=(20+1)+(20+2)+(20+3)+....+(20+40)
  =(20*40)+(1+2+3+....+40)
  =800+820
  =1620
• 8 years agoHelpfull: Yes(4) No(1)
• (21+22+23........+60)
  here,
  n(n+1)/2 - n(n+1)/2
  (60x61)/2 - (20x21)/2
  1830-210
  =1620
• 8 years agoHelpfull: Yes(2) No(0)