
Chapter 11: SERIES COMPLETION
Introduction
This involves recognizing the next term in a series and
choosing one from the alternatives given.
Q. 7 , 12 , 19 , X , 39
A. X = 28 as the series follows the pattern:
7, 7+5, 12+7, 19+9, 28+11 where the number is added by the
next odd number.
Q. 0, 6, 24, 60, 120, 210, X
A. X = 336 as series follows pattern 1^{3}1
, 2^{3}2 , 3^{3}3 , 4^{3}4....
Q. 4 , 6 , 12 , 14 , 28 , 30 , X
A. There are 2 series in this series 4, 12,
28 ... and 6, 14, 30 and both follow pattern +8, +16, +32, So
we get missing value as 28+32 = 60
Q. 1, 4, 9, 16, 25, X
A. Series follows pattern: +3, +5, +7, +9
...
Q. 20, 19, 17, X, 10, 5
A. Series follows pattern: 1, 2, 3, 4,
5
Q. 6, 11, 21, 36, 56...
A. Pattern: +5, +10, +15, +20, +25...
Q. 1, 6, 13, 22, 33, ...
A. Pattern: +5, +7, +9, +11 ...
Q. 1, 9, 17, 33, 49, 73, X
A. Pattern: + 4 * 2, + 4 * 2, + 4 * 4, + 4 *
4, + 4 * 6, + 4 * 6
Q. 0.5, 1.5, 4.5, 13.5, X
A. Pattern: + 1 , + 1 * 3, + 3 * 3, + 9 * 3
; Multiply the previous value obtained by 3 each time.
Q. 19, 2, 38, 3, 114, 4, X
A. There are two series: 2, 3, 4, ... and
19, 38, 114, X. The second series follows patterns: * 2, * 3 ,
* 4, ... So answer is 114*4 = 456
Choose the wrong alternative
Q. 7, 28, 63, 124, 215, 342, 611 ..
A. Series follows pattern: 2^{3} 
1, 3^{3}1, 4^{3}1, 5^{3}1 ... Now
we have to check which term doesn't fit this pattern.
Q. 3, 8, 15, 24, 34, 48, 63 ...
A. Series pattern: next term  previous term
= 5, 7, 9 ...
Q. 196, 169, 144, 121, 80
A. Pattern: 14^{2}, 13^{2},
12^{2}, 11^{2} ...
Q. 121, 143, 165, 186, 209
A. Pattern: 11^{2} 0^{2},
12^{2}1^{2}, 13^{2}2^{2}, 14^{2}
 3^{2}, 15^{2}  4^{2} . Thus odd
term is 186.
^{
}Q. 1, 2, 4, 8, 16, 32, 64, 96
A.^{ }96 as it is not double of
previous
Q. 1, 3, 7, 15, 27, 63, 127
A. Series pattern: +2, +4, +8, +16 .... 27
doesn't follow this pattern.
Q. 6, 14, 30, 64, 126 ...
A. Pattern: +8, +16, +32, +64 and 64 breaks
the pattern.
Q. 1236, 2346, 3456, 4566, 5686
A. 5686 breaks the pattern; The first three
digits form continuous series so last number should be 5676.
Q. 5, 10, 40, 80, 320, 550, 2560
A. Series follows the pattern: *
2, * 4, * 2, * 4 ....
Q. 11, 2, 21, 3, 32, 4, 41, 5, 51, 6
A.^{ }There
are two series: 2, 3, 4, 5.. 11 , 21 , 31 , 41 , 51. 32 breaks
the second series.
Alphabet Series
Alphabet series sums can be solved using this diagram as
reference.
Q. ' ' , ' ', R, T, V, X, Z
A. Series starts from N and skips one
alphabet.
Q. P, K, G, D, B, A
A. Series has the pattern:  5, 4, 3 , 2
...
Q. BDF, CFI, DHL, ....
A. The first term is moved one place ahead,
second two places and third three places.
Q. YEB, WFD, UHG, SKI .....
A. The first term is moved back by 1 then 2
then 3 steps. The second and third terms are moved forward by
1 then 2 then 3 steps. Missing term :QOL
Q. AB, DG, HM, MT, SB, ...
A. The first term is moved ahead in pattern
+2, +3, +4 ... The second term is moved ahead in pattern: +4,
+5, +6...
Q. P3, R5, T8, V12, ...
A. The first term is moved ahead by +1, +2,
+3 and second term by +2, +3, +4 ...