Q. Find the next number in the series 1 ,7, ,21 ,42,...?

• 1=0^2+1
  7=2^2+3
  21=4^2+5
  42=6^2+7
  73=8^2+9
• 10 years agoHelpfull: Yes(34) No(25)
• 7 - 1 = 6
  21- 7 = 14
  42- 21= 21
  
  6 , 14 , 21
  14 - 6 = 8
  21 - 14= 7
  
  so next difference will be 6
  27 - 21= 6
  
  so next number will be 42 + 27 = 69
• 10 years agoHelpfull: Yes(29) No(6)
• 1,7,21,42,......
  excpt 1..
  7*3=21
  7*6=42
  7*9=63(ans)
  
• 9 years agoHelpfull: Yes(4) No(0)
• 7 - 1 = 6
  21- 7 = 14
  42- 21= 21
  
  6 ,14,21
  14=6*2+2
  21=6*3+3
  so next difference will be 6*4+4=28
  hence next term=42+28=70
  
• 9 years agoHelpfull: Yes(1) No(0)
• 1,7,21,42,84
• 10 years agoHelpfull: Yes(0) No(9)
• i.e 42*3 126
• 4 years agoHelpfull: Yes(0) No(0)