Series Completion Questions Answers

29. 6, 11, 21, 36, 56, ... ?
 81
 83
 95
 105
Answer And Explanation
Answer: Option A
Explanation:
Pattern is +5, +10, +15, + 20. So next will be 56+25 = 81

30. 5, 9, 17, 29, 45, ... ?
 58
 64
 65
 80
Answer And Explanation
Answer: Option C
Explanation:
Pattern in the series is +4, +8, +12, +16.
Next term will be 45 + 20 = 65 
31. 20, 19, 17, (...) , 10, 5
 16
 12
 15
 14
Answer And Explanation
Answer: Option D
Explanation:
Pattern in the series is 1, 2, .., .. , 5
So next term will be 17  3 = 14 
32. 13, 35, 57, 79, 911, ?
 1005
 1110
 1113
 1140
Answer And Explanation
Answer: Option C
Explanation:
The terms of the given series are numbers formed by joining together consecutive odd numbers in order i.e. 1 and 3, 3 and 5, 5 and 7, 7 and 9, 9 and 11, .....
So, missing term = number formed by joining 11 and 13 = 1113. 
33. 4, 10, (?), 82, 244, 730
 26
 28
 40
 48
Answer And Explanation
Answer: Option B
Explanation:
Each number in the series is the preceding number multiplied by 3 and then decreased by 2.

34. In the series 3, 9, 15.. what will be the 21st term ?
 123
 126
 129
 136
Answer And Explanation
Answer: Option A
Explanation:
We can judge that it is A.P.
With 6 as difference
nth term in A.P. = a+(n1)d
a= 3, n = 21, d = 6
So, 21st term will be = 3+(20)6 = 123

35. In the series 2, 6, 18, 54, ... what will be the 8th term ?
 4174
 4150
 4274
 4374
Answer And Explanation
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^{n1} \\
= 2*3{81} \\
= 2*3^7 \\
= 2*2187 = 4374
\end{aligned}