9,18,21,25,20,?

• ans is 21
  9,18 diff is 9=3^2
  21,25 diff is 4=2^2
  next diff must be 1^2=1 so 20,21
• 10 years agoHelpfull: Yes(23) No(4)
• Ans: 30
  Exp:
  9,18,21,25,20,?
  3*3=9
  3*6=18
  3*7=21
  Similarly....
  5*5=25
  5*6=30
• 11 years agoHelpfull: Yes(11) No(65)
• 9+(3*3)=18
  21+(2*2)=25
  20+(1*1)=21
• 9 years agoHelpfull: Yes(11) No(3)