SSC CGL 2024 Tier-I · 13 September 2024, Shift 3 · General Intelligence and Reasoning · Question 21 of 98

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 6 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Select the option that represents the letters that when sequentially placed from left to right in the blanks below will complete the letter series. _ O _ O _ _ O _ P _ O _

(a)PPOOPOP
(b)OOPPPOO
(c)OPOPOOP
(d)PPOOOPO

Answer

Why

Correct — C. The series has twelve places and seven blanks. Find the repeating unit before testing anything.

The printed letters are O at place 2, O at 4, O at 7, P at 9 and O at 11. A P at place 9 with Os at 2, 4, 7 and 11 fits a unit of three.

Rule: the string is O O P written out four times over, so P falls at places 3, 6, 9 and 12 and every other place is O.

Option (c) is O P O P O O P. Dropping those into blanks 1, 3, 5, 6, 8, 10, 12 in order gives O O P | O O P | O O P | O O P, and every printed letter lands exactly where it already was.

Why the others are wrong

(a)
PPOOPOP — Its first letter puts P at place 1, but the unit opens O O P, so place 1 is an O. It also strands a P at place 8, where the third unit needs an O.
(b)
OOPPPOO — It opens correctly with O, then its second letter puts O at place 3 — the P that closes the first unit. The line would begin O O O O.
(d)
PPOOOPO — P at place 1 again, and its sixth letter puts a P at place 10. The line would end P P O O instead of P O O P.

Concept

Blank-filling letter series are built from a short unit repeated to fill the line. The work is finding that unit, not testing options one at a time.

Count the places first — twelve here. Then read the printed letters as constraints: P appears at place 9, and O at places 2, 4, 7 and 11.

A unit of three fits all five. P at place 9 means P sits at every third place, so it takes 3, 6, 9 and 12 and everything else is O. That gives O O P, written out four times over.

The instruction says the letters go into the blanks sequentially from left to right, so the number of blanks and the number of letters in an option must match before anything else is checked. Seven blanks, seven letters.

Key facts

The completed series is O O P O O P O O P O O P.
P occupies places 3, 6, 9 and 12 and no others.
The seven blanks are at places 1, 3, 5, 6, 8, 10 and 12.

Study next

Letter series built from a repeating unit whose length divides the number of placesSeries using three distinct letters instead of twoSeries where the repeating unit itself shifts by one letter each cycle

Common traps

Testing options left to right without first working out the repeating unit.
Miscounting the blanks, so the seven letters land one place out.
Assuming O and P simply alternate — that reading puts a P at place 7, which is printed as O.

A near-identical shape, with three letters instead of two, is set at 13 Sep 2024, 09:00, Reasoning Q.14, and a longer five-letter version at 11 Sep 2024, 16:00, Reasoning Q.3.

Related PYQs

No directly related past PYQ was found.