1,2,3,5,7,10,13,17,_

• Ans. 21
  The difference between 1 and 2 = 1. And difference between 3 and 2 = 1.
  Similarly the difference between 5 and 3 = 2. And the difference between 7 and 5 = 2.
  Next the difference between 10 and 7 = 3 and 13 and 10 =3.
  And the difference between 17 and 13 = 4. So the next digit after 17 must be at a difference of 4. Thus 17 + 4 = 21.
• 9 years agoHelpfull: Yes(56) No(2)
• ANS IS 21
  1+1=2
  2+1+3
  3+2=5
  5+2=7
  7+3 =10
  10+3=13
  13+4=17
  17+4=21
• 9 years agoHelpfull: Yes(17) No(1)
• 21
  +1 +1 +2 +2 +3 +3 +4 +4 etc
  
  
• 9 years agoHelpfull: Yes(4) No(1)
• 1st series:1,3,7,13,21,....difference:2,4,6,8...
  2nd series:2,5,10,17,26,....difference:3,5,7,9...
• 9 years agoHelpfull: Yes(3) No(0)
• 1+1=2
  2+1=3
  3+2=5
  5+2=7
  7+3=10
  10+3=13
  13+4=17
  17+4=21
  
• 9 years agoHelpfull: Yes(2) No(0)
• ans is 21
  1+1=2
  2+1+3
  3+2=5
  5+2=7
  7+3=10
  10+3=13
  13+4=17
  17+4=21
• 9 years agoHelpfull: Yes(2) No(0)
• 21.
  Explanation if we break d above series in two sub series i.e
  1,3,7,13 i.e
  3=2+1
  7=4+3
  13=6+7
  so d next term will be
  13+8=21 (multiple of 2).
• 9 years agoHelpfull: Yes(1) No(1)
• 19 bcz of prime numbers
• 9 years agoHelpfull: Yes(1) No(18)
• 21, after 1,1+1,2+1,3+2,5+2,7+3,10+3,13+4,17+4=21
• 9 years agoHelpfull: Yes(1) No(0)
• asw=22
  (1+2)-0=3
  (2+3)-0=5
  (3+5)-1=7
  (5+7)-2=10
  7+10-4=13
  10+13-6=17
  17+13-8=22
  
  
  
• 9 years agoHelpfull: Yes(1) No(3)
• 1 and 2 difference = 2 and 3 difference
  3 and 5 difference = 5 and 7 difference
  7 and 10 difference = 10 and 13 difference
  13 and 17 difference = 17 and 21 difference
  ans: 21
• 7 years agoHelpfull: Yes(1) No(0)
• 1,3,7,13,21(difference between digit is increase by 2)
  2,5,10,17(difference between digit is increase by 2)
• 7 years agoHelpfull: Yes(1) No(0)
• 21
  (1+1=2), (2+1=3), (3+2=5), (5+2=7), (7+3=10), (10+3=13), (13+4=17), (17+4=21)
• 9 years agoHelpfull: Yes(0) No(1)
• ans is 21.
  for the first&second number add 1,for the 3rd&4th number add 2 like that for 17 add 4.
• 9 years agoHelpfull: Yes(0) No(0)
• 1(0)2(0)3(4)5(6)7(8,9)10(11,12)13(14,15,16)17(18,19,20)21
  21 is answer
• 9 years agoHelpfull: Yes(0) No(0)
• it is alternate series please check carefully 1,3,7,13,,21 because gap b/w 1 to 3 is 2,3 to 7 is 4,7 to 17 is 6 then 13 to 21 is 8 so it must be 21.
• 9 years agoHelpfull: Yes(0) No(0)
• their are 2 series in the sequence
  1+2=3,3+4=7,7+6=13(add answer with even numbers)
  2 +3=5,5+5=10,10+7=17(add answer with odd number)
  so the answer is 13+8=21
• 9 years agoHelpfull: Yes(0) No(0)
• 21...diff b/w 2 and 1 is 1 and 3 and 2 is 1,diff b/w 5 and 3 is 2 in d same way diff b/w 7 and 5 is 2...lyk wise diff b/w 13 and 10 is 3.......diff b/w 21 and 17 is 4
• 9 years agoHelpfull: Yes(0) No(0)
• 1+1=2
  2+1=3
  3+2=5
  5+2=7
  7+3=10
  10+3=13
  13+4=17
  17+4=21
  i.e. 21 is answer
• 9 years agoHelpfull: Yes(0) No(0)
• 2-1=1, 3-2=1
  5-3=2, 7-5=2
  10-7=3, 13-10=3
  17-13=4, so 21-17=4
  Answer is 21
• 9 years agoHelpfull: Yes(0) No(0)
• alternate:1,3,7,13 is diffrence=2+4+6....8=21ans
  2,5,10,17 is3,5,7....................
• 9 years agoHelpfull: Yes(0) No(0)
• 1+1=2,2+1=3,+2=5,+2=7,+3=10,+3=13,+4=17,+4=21
  ans is 21
• 9 years agoHelpfull: Yes(0) No(0)
• ANS IS 21
  1+1=2
  2+1+3
  3+2=5
  5+2=7
  7+3 =10
  10+3=13
  13+4=17
  17+4=21
• 9 years agoHelpfull: Yes(0) No(0)
• 21
  1+1=2+1=3
  3+2=5+2=7
  7+3=10+3=13
  13+4=17+4=21
• 8 years agoHelpfull: Yes(0) No(0)
• find the differences
  1-2=1
  2-3=1
  3-5=2
  5-7=2
  7-10=3
  10-13=3
  13-17=4
  17-21=4
  answer :21
• 8 years agoHelpfull: Yes(0) No(0)
• ans=21
  1 2 3 (4) 5 (6) 7 (8)(9) 10 (11)(12) 13 (14)(15)(16) 17 (18)(19)(20) 21
  skip all nos in brackets
• 8 years agoHelpfull: Yes(0) No(0)
• ans is 21
  
  first two is gap 1
  next two is 2 gap
  and next two again 3
  and other next will 4
  17+4=21
• 8 years agoHelpfull: Yes(0) No(0)
• 1+1=2
  2+1=3
  3+2=5
  5+2=7
  7+3=10
  10+3=13
  13+4=17
  17+4=21
• 8 years agoHelpfull: Yes(0) No(1)
• 21 2-1,3-2 difference 1, 5-3,7-5 difference 2 10-7,13-10 difference 3 17-13,21-17 difference 4
• 8 years agoHelpfull: Yes(0) No(1)
• It will be 21
• 7 years agoHelpfull: Yes(0) No(0)
• 2-1=1
  3-2=1
  5-3=2
  7-5=2
  10-7=3
  13-10=3
  17-13=4
  21-17=4
• 6 years agoHelpfull: Yes(0) No(0)
• next number in series is 21
• 6 years agoHelpfull: Yes(0) No(0)
• 1+1=2
  2+1+3
  3+2=5
  5+2=7
  7+3 =10
  10+3=13
  13+4=17
  17+4=21
  answer is 21
• 6 years agoHelpfull: Yes(0) No(0)
• the difference between 1 and 2 is =1 . and difference between 3 and 2=1
  sim,the difference between 5 and 3 is 2. and diff between 7 and 5 is 2
  10 and 7 is 3 and 13 and 10=3
  diff between 17 and 13=4
  after 17 must be at a difference of 4 .then 17+4=21
• 4 years agoHelpfull: Yes(0) No(0)