Consider the sequence AB_CC_A_BCCC_BBC_C that follows a certain pattern. Which one of the following completes the sequence?
Reviewed by Dalvoy
UPSC Civil Services preparation
- AB, C, B, C, A
- BA, C, B, C, A
- CB, C, B, A, CCorrect
- DC, B, B, A, C
Explanation
The given sequence is: AB_CC_A_BCCC_BBC_C
First, let's count the total number of positions (including blanks) in the sequence.
A (1) B (2) _ (3) C (4) C (5) _ (6) A (7) _ (8) B (9) C (10) C (11) C (12) _ (13) B (14) B (15) C (16) _ (17) C (18)
There are 18 positions in total, with 5 blanks.
Now, let's try filling the blanks with the letters from Option C: B, C, B, A, C.
The blanks are at positions 3, 6, 8, 13, and 17.
1. Fill the 1st blank (position 3) with 'B'.
2. Fill the 2nd blank (position 6) with 'C'.
3. Fill the 3rd blank (position 8) with 'B'.
4. Fill the 4th blank (position 13) with 'A'.
5. Fill the 5th blank (position 17) with 'C'.
The sequence becomes:
A B (B) C C (C) A (B) B C C C (A) B B C (C) C
Let's write out the complete sequence after filling the blanks:
A B B C C C A B B C C C A B B C C C
Now, observe the pattern in this completed sequence. It can be clearly divided into three identical blocks:
(A B B C C C) (A B B C C C) (A B B C C C)
Each block is "ABBC CC", which is 6 characters long. Since there are three such blocks, the total length is 3 * 6 = 18 characters, matching the total positions in the sequence. This indicates a consistent repeating pattern.
Let's briefly check why other options are incorrect:
If we fill with Option A (B, C, B, C, A): A B B C C C A B B C C C C B B C A C - No clear repeating pattern.
If we fill with Option B (A, C, B, C, A): A B A C C C A B B C C C C B B C A C - No clear repeating pattern.
If we fill with Option D (C, B, B, A, C): A B C C C B A B B C C C A B B C C C - No clear repeating pattern.
Thus, Option C is the only one that completes the sequence to form a logical and consistent repeating pattern.
The final answer is C

Related questions
More UPSC Prelims practice from the same subject and topic.
- Prelims 2025CSATLogical Reasoning
What comes at X and Y respectively in the following sequence? January, January, December, October, X, March, October, Y, September
- Prelims 2025CSATLogical Reasoning
What is X in the sequence 24, X, 12, 18, 36, 90 ?
- Prelims 2025CSATLogical Reasoning
What is X in the sequence 1, 3, 6, 11, 18, X, 42?
- Prelims 2025CSATLogical Reasoning
If 7*24 = 25 and 12*16 = 20 , then what is 16*63 equal to?
- Prelims 2025CSATLogical Reasoning
Consider the following statements: I. If A≤ B > C E > F≥ G = H ; then B is always greater than E. II. If P > Q = R≥ S = T≤ U = V > W ; then S is always less than V. Which of the statements given above…
- Prelims 2025CSATLogical Reasoning
If P = + , Q = - , R = × , S = ÷ , then insert the proper notations between the successive numbers in the equation 60\_ 15\_ 3\_ 20\_ 4 = 20 :