Find the next number in series....
1, 3, 6, 10, 15

• 1
  1+2=3
  1+2+3=6
  1+2+3+4=10
  1+2+3+4+5=15
  1+2+3+4+5+6=21
• 9 years agoHelpfull: Yes(23) No(0)
• it is of the form n(n+1)/2
  1(2)/2 = 1
  2*3/2 = 3
  3*4/2 = 6
  4*5/2 = 10
  5*6/2 = 15
  6*7/2 = 21
  
  so the next number will be 21
• 9 years agoHelpfull: Yes(9) No(0)
• see the each number with its precceding numbers
  1--->3 difference 2
  3--->6 difference 3
  6--->10 difference 4
  10-->15 difference 5
  so the next number will be with difference 6 so add 6 to 15 then 15+6=21
  answer:21
• 9 years agoHelpfull: Yes(6) No(0)
• 21
  3=1st num+2
  6=2ndnum + 3
  10=3rdnum +4 and so on
• 9 years agoHelpfull: Yes(2) No(0)
• 21
  difference of number
  1 - 3= -2
  3 - 6= -3
  6 - 10= -4
  10 - 15= -5
  15 - 21 = -6
• 9 years agoHelpfull: Yes(2) No(0)
• numbers from 2 are getting added to the previous digit to get the next digit
  like 1+2=3
  3+3=6
  6+4=10
  10+5=15
  15+6=21
• 9 years agoHelpfull: Yes(1) No(0)
• Diff between
  3-1=2
  6-3=3
  10-6=4
  15-10=5
  ?-15=6
  (21-15=6)
  Ans is 21
• 9 years agoHelpfull: Yes(1) No(0)
• 21..the series follows the logic 1+2=3,3+3=6,6+4=10,10+5=15....and so on..
• 9 years agoHelpfull: Yes(1) No(0)
• 1+2=3
  3+3=6
  6+4=10
  10+5=15
  15+6=21
  ans is 21
• 9 years agoHelpfull: Yes(1) No(0)
• 1+2=3
  3+3=6
  6+4=10
  10+5=15
  15+6=21
  
• 9 years agoHelpfull: Yes(1) No(0)
• 1+2=3
  3+3=6
  6+4=10
  10+5=15
  15+6=21
• 9 years agoHelpfull: Yes(1) No(0)
• 1
  1+2=3
  3+3=6
  6+4=10
  10+5=15
  15+6=21
  
• 9 years agoHelpfull: Yes(1) No(0)
• 1,3,6,10,15.....
  so next term will be 21
  
• 9 years agoHelpfull: Yes(0) No(1)
• ans: 21
  15+6
• 9 years agoHelpfull: Yes(0) No(0)
• 1
  3-1=2
  6-3=3
  10-6=4
  15-10=5
  21-15=6
  so ans is 21
• 9 years agoHelpfull: Yes(0) No(0)
• 3-1=2
  6-3=3
  10-6=4
  15-10=5
  21-15=6
  ans:-21
• 9 years agoHelpfull: Yes(0) No(0)
• 1+2=3
  3+3=6
  6+4=10
  10+5=15
  15+6=21..
  So Ans is 21
• 9 years agoHelpfull: Yes(0) No(0)
• The difference between first two number is 2 then 3 and so on.
  Ans:21
• 9 years agoHelpfull: Yes(0) No(0)
• 21...
  1+2=3
  3+3=6
  6+4=10
  10+5=15
  15+6=21
• 9 years agoHelpfull: Yes(0) No(0)
• 3-1=2
  6-3=3
  10-6=4
  15-10=5
  21-15=6
  ans is 21
• 8 years agoHelpfull: Yes(0) No(0)