Series Completion Problems and Answers

• 15. 20, 19, 17, (...) , 10, 5

  1. 16
  2. 12
  3. 15
  4. 14

  Answer :

  Option D

  Explanation:

  Pattern in the series is -1, -2, .., .. , -5
  
  So next term will be 17 - 3 = 14

• 16. 5, 9, 17, 29, 45, ... ?

  1. 58
  2. 64
  3. 65
  4. 80

  Answer :

  Option C

  Explanation:

  Pattern in the series is +4, +8, +12, +16.
  Next term will be 45 + 20 = 65

• 17. 8, 9, 8, 7, 10, 9, 6, 11, 10, (...), 12

  1. 7
  2. 6
  3. 5
  4. 4

  Answer :

  Option C

  Explanation:

  Please note that above sequence is containing 3 series
  Series 1 : 8, 7, 6, (..)
  Series 2 : 9, 10, 11, 12
  Series 3 : 8, 9, 10
  
  In series 1 pattern is -1. So missing term will be 6-1 = 5
  

• 18. Which number would replace the question mark in series
  7,12,19,?,39

  1. 24
  2. 28
  3. 31
  4. 33

  Answer :

  Option B

  Explanation:

  Pattern is , +5, +7, +9
  Missing Number = 19+9 = 28

• 19. Look at this series: 22, 21, 23, 22, 24, 23, ... What number should come next?

  1. 25
  2. 26
  3. 27
  4. 28

  Answer :

  Option A

  Explanation:

  Please look carefully at the series, its pattern is,
  -1, +2, -1, +2, -1, so next will be +2
  23+2 = 25

• 20. 2,5,9,?,20,27, what will replace the question mark ?

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

  Answer :

  Option B

  Explanation:

  Pattern is +3,+4,..,..,+7, so +5 and +6 will be in the blanks
  
  Question mark will be replaced by 9+5 = 14

• 21. In the series 2, 6, 18, 54, ... what will be the 8th term ?

  1. 4174
  2. 4150
  3. 4274
  4. 4374

  Answer :

  Option D

  Explanation:

  We can see the given series is in G.P.
  as 2*3 = 6, 6*3 = 18, 18*3 = 54
  So a = 2 , r = 3
  nth term in G.P. is
  \begin{aligned}
  ar^{n-1} \\
  = 2*3{8-1} \\
  = 2*3^7 \\
  = 2*2187 = 4374
  \end{aligned}