Series Completion Problems and Answers

• 29. 6, 11, 21, 36, 56, ... ?

  1. 81
  2. 83
  3. 95
  4. 105

  Answer :

  Option A

  Explanation:

  Pattern is +5, +10, +15, + 20. So next will be 56+25 = 81

• 30. 6, 11, 21, 36, 56, ?
  what will replace the question mark in the series ?

  1. 75
  2. 81
  3. 85
  4. 89

  Answer :

  Option B

  Explanation:

  Pattern is +5, +10, + 15, +20
  
  Next number in the series will be 56 + 25 = 81

• 31. Complete the series
  20, 19, 17, ...., 10, 5

  1. 15
  2. 16
  3. 13
  4. 14

  Answer :

  Option D

  Explanation:

  Pattern is, -1, -2, ..,.. , -5
  
  So -3 and -4 will fill the blanks to make it a pattern.
  
  Next number will be 17-3 = 14

• 32. In the series 3, 9, 15.. what will be the 21st term ?

  1. 123
  2. 126
  3. 129
  4. 136

  Answer :

  Option A

  Explanation:

  We can judge that it is A.P.
  With 6 as difference
  nth term in A.P. = a+(n-1)d
  a= 3, n = 21, d = 6
  So, 21st term will be = 3+(20)6 = 123
  

• 33. 1,6,15,(...),45,66,91

  1. 26
  2. 28
  3. 29
  4. 34

  Answer :

  Option B

  Explanation:

  Pattern in the series is, +5, +9, .., .., +21, +25
  So 4 is getting increased at every term addition.
  Missing term in the series will be 15+(9+4)
  = 15+13 = 28

• 34. 1,1,3,9,6,36,10,100,(..),225

  1. 12
  2. 13
  3. 14
  4. 15

  Answer :

  Option D

  Explanation:

  Given sequence is combination of two series
  Series 1 : 1,3,6,10,..
  Series 2 : 1,9,36,100,225
  
  In series 1 pattern is +2, +3, +4. So next term will be
  10+5 = 15

• 35. 21,25,33,49,81, ?

  1. 140
  2. 145
  3. 147
  4. 159

  Answer :

  Option B

  Explanation:

  Pattern is, +4, +8, +16, +32, so next will be +64
  81+64 = 145