Logical Reasoning Quest
Number Series
Find out the missing number in the following sequence : 1, 3, 3, 6, 7, 9, ?,
12, 21.
(1) 10
(2) 11
(3) 12
(4) 13
Sol. Clearly, the given sequence is a combination of two series :
I. 1, 3, 7, ?, 21 and II. 3, 6, 9, 12
The pattern followed in I is + 2, + 4, ...; and the pattern followed in II is
+3. Thus, missing number = 7 + 6 = 13.
Hence, the answer is (4).