find the next number in the series:
1,3,7,13,21,31,.....
a)43
b)33
c)41
d)45

• a) 43
  (1+2),(3+4),(7+6),(13+8),(21+10),(31+12)
• 10 years agoHelpfull: Yes(12) No(3)
• 1,3,7,13,21,31 each have diff is 2,4,6,8,10 and next will be 12 so next no is 31+12=43
• 10 years agoHelpfull: Yes(7) No(0)
• ANS : Option A 43
  1+2 = 3
  3+4 = 7
  7+6 = 13......
  An = A(n-1) + 2*(n-1) (for n>1)
  Therefore A7 = A6 + 2*6 = 31 + 12 = 43
  
• 10 years agoHelpfull: Yes(6) No(0)
• difference b/w 2 nos increasing in order of 2,4,6,8,10,12....
  21-13=8
  31-21=10
  x-31=12
  hence x is 43
• 10 years agoHelpfull: Yes(3) No(1)
• we have adding in the sequence 2 , 4 , 6 , ....
  hence the missing number is 12
  so, 31+12=43
• 10 years agoHelpfull: Yes(2) No(0)
• sol:43
  1,3,7,13,21,31,?
  the difference between every two no's is 2,4,6,8,10,? i.e,12
  then the missing term is 31+12=43.
• 10 years agoHelpfull: Yes(1) No(0)
• 1,3,7,13,21,31,?
  1^2-0,2^2-1,3^2-2,4^2-3,5^2-4,6^2-5,and the next number would be 7^2-6=49-6=43
• 10 years agoHelpfull: Yes(1) No(0)
• 43... the difference between the numbers in the given series is even numbers...
• 10 years agoHelpfull: Yes(0) No(3)
• a-43
  1+2=3+4=7+6=13+8=21+10=31+12=43
  
• 10 years agoHelpfull: Yes(0) No(0)
• 1+2=3
  3+4=7
  7+6=13
  13+8=21
  21+10=31
  31+12=43
  Add the even number to the corresponding results were produced Hence the answer is 43
• 10 years agoHelpfull: Yes(0) No(0)
• 1+2=3+4=7+6=13+8=21+10=31+12=43
• 10 years agoHelpfull: Yes(0) No(0)
• 43
  reason:the difference between the two consecutive room are in the sequence 2,4,6,8,10,12,..........
• 10 years agoHelpfull: Yes(0) No(0)
• a; diff b/w consecutive numbers is even atlast the no. is 12 so 31+12=43
  
  
• 10 years agoHelpfull: Yes(0) No(0)
• a)43
  serial no is in interval of 1,3,5,7,11...in between the numbers.
  
• 10 years agoHelpfull: Yes(0) No(0)
• ans is 43, since difference between the numb is 2,4,6,8,10,12......
• 10 years agoHelpfull: Yes(0) No(0)
• ans is 43
  if the first no is added with even no 2 we will get the next no
  likewise if we add the ans with incrementing the even no by 2 each time we will get the seies i.e.
  1+2=3
  3+4=7
  7+6=13
  13+8=21
  21+10=31
  31+12=43
• 10 years agoHelpfull: Yes(0) No(0)
• common difference is even numbers from 2
  31+12 =43
• 10 years agoHelpfull: Yes(0) No(0)
• 2^2-1,3^2-2...............7^2-6
• 9 years agoHelpfull: Yes(0) No(0)
• a)43
  1+2=3,3+4=7,7+6=13,13+8=21,21+10=31,31+12=43
  so 43 ans...
• 8 years agoHelpfull: Yes(0) No(0)
• 3-1 = 2
  7-3 = 4
  13-7 = 6
  21-13 =8
  31-21 =10
  
  so 31+12 = 43
• 8 years agoHelpfull: Yes(0) No(0)
• between 1 and 3, 3 and 7, 7 and 13 there are only one other prime number. between 13 and 21, 21 and 31 there are two prime nos. hence between 31 and 43 there are two prime nos. viz. 37 and 41.....
• 8 years agoHelpfull: Yes(0) No(0)
• 43
  1+2=3
  3+4=7
  7+6=13
  13+8=21
  21+10=31
  31+12=43
• 5 years agoHelpfull: Yes(0) No(0)
• Each number in the series is followed by the even number difference..
  That is 3-1=2
  7-3=4
  13-7=6
  .
  .
  .
  31-21=10
  43-31=12
• 4 years agoHelpfull: Yes(0) No(0)
• 1 +2 = 2
  3 +4 =7
  7 +6 =13
  13 +8 =21
  21 +10=31
  31 +12 =43
  
  
  
  Ans = 43
• 4 years agoHelpfull: Yes(0) No(0)
• 43....we are taking the odd series
• 4 years agoHelpfull: Yes(0) No(0)