Reasoning and computer aptitude in the IBPS Clerk mains

Clearing the prelims gets you into the mains. The mains decides whether you get the job, and in the mains a reasoning question is worth more than a question in any other section. The same section also carries the computer questions, which are among the fastest marks in the paper if you have learnt them.

So this section rewards two kinds of preparation: puzzle method, built over weeks, and computer facts, learnt like awareness. This guide covers both, with a full mains-level puzzle solved the way you should solve it in the hall.

How the section is set

The penalty matters more here than in the prelims. A wrong answer costs 0.375 marks, so a careless puzzle set with five wrong answers costs you almost 2 marks on top of the 7.5 you did not earn.

What changes from the prelims

The skills are the same. What changes is the number of clues you must hold at once, and the number of cases a clue can open. The answer is not speed but order: definite clues first, then clues that link to them, then negative clues.

A mains-level puzzle, solved

Seven people, A, B, C, D, E, F and G, live on the seven floors of a building, one on each floor. The lowest floor is 1 and the top floor is 7. Each likes a different colour: Red, Blue, Green, Yellow, White, Black and Pink.

1. Only two people live between C and the person who likes White, and the person who likes White lives above C.
2. A lives immediately below the person who likes White.
3. The person who likes Pink lives immediately below C.
4. F lives immediately above C.
5. Only one person lives between B and G, and B lives below G.
6. Only one person lives below the person who likes Blue.
7. D lives on a floor above A.
8. E lives on an even-numbered floor.
9. The person who likes Red lives immediately above the person who likes Black.
10. A does not like Yellow.
11. The person who likes Black lives on an even-numbered floor.

Step 1: take the only fully definite clue. Clue 6 says exactly one person is below the Blue person, so Blue is on floor 2.

Step 2: chain the clues that hang on C. Clues 1 to 4 all describe positions relative to C. If C is on floor x, then F is on x + 1, A on x + 2, White on x + 3 and Pink on x − 1. White must fit in the building, so x is at most 4, and Pink must fit, so x is at least 2. That leaves three cases.

Step 3: test the cases.

• C on 3: Pink would be on floor 2, but floor 2 is Blue. Rejected.
• C on 2: F is on 3, A on 4, White on 5, Pink on 1. B, D, E and G take floors 1, 5, 6 and 7. E must be on an even floor, so E is on 6. G is two floors above B, and the only such pair left is B on 5 and G on 7. That puts D on 1, below A, which breaks clue 7. Rejected.
• C on 4: F is on 5, A on 6, White on 7, Pink on 3. D must be above A, so D is on 7. E takes the even floor 2, so B is on 1 and G on 3. Clue 5 holds.

Step 4: finish the colours. Black must be on an even floor, and floor 2 is Blue, so Black is on 4 or 6. If Black were on 6, Red would be on 7, which is White. So Black is on 4 and Red on 5. Green and Yellow remain for floors 6 and 1, and A does not like Yellow, so A likes Green and B likes Yellow.

Questions on this set:

1. Who lives immediately above the person who likes Pink? C. Pink is G on floor 3, and floor 4 is C.
2. How many people live between E and F? Two. E is on 2 and F on 5, so floors 3 and 4 lie between them.
3. Which pair is correctly matched? (a) G, Blue (b) F, Red (c) C, Green (d) D, Black. (b). G likes Pink, C likes Black and D likes White.

Coded inequality, worked

The mains often hides the inequality signs behind symbols. Decode first, then solve as usual.

Suppose P @ Q means P > Q, P # Q means P < Q, P % Q means P ≥ Q and P & Q means P = Q.

Statement: M @ N, N % R, R & S

Conclusions: I. M @ S II. N @ S III. N & S

1. Decode: M > N ≥ R = S.
2. I says M > S. The chain runs one way with a strict sign in it, so M > S. I follows.
3. II says N > S and III says N = S. From N ≥ R = S we only know N ≥ S, so neither follows alone.
4. II and III are about the same pair, and together they cover every case of N ≥ S. So either II or III follows.

Data sufficiency, worked

Question: Among five friends J, K, L, M and N, who is the tallest?

• I. J is taller than K and L but shorter than M.
• II. N is shorter than L.

1. I alone: M > J, and J > K, J > L. N is never compared, so M or N could be tallest. Not sufficient.
2. II alone: only N and L are compared. Not sufficient.
3. Together: M > J > L > N, and J > K. M is taller than everyone. Both statements together are needed.

Test each statement alone before you combine them, and never carry a fact from one into the other while testing alone. More types are in the data sufficiency guide.

Computer aptitude

Most computer questions are direct facts. You know the answer in five seconds or you do not, so they suit the start of the section.

The computer topics have their own computer plan. Two to three weeks of steady study covers the common questions.

A 35-minute plan

Treat this as a starting point. Adjust it after three or four full mocks to match your own strengths.

Common mistakes

• Starting with the first puzzle on the screen instead of the one with the most definite clues.
• Leaving computer questions to the end, when they are quick marks.
• Guessing in a puzzle set you did not solve. At 0.375 per wrong answer, five wrong guesses cost 1.875 marks, more than one correct answer earns.
• Not rejecting a case explicitly, then mixing two cases in the final diagram.

A four-week plan before the mains

What to do next

• Re-solve the floor puzzle above without looking, and time yourself.
• Make a one-page computer fact sheet this week and read it daily.
• Solve two mains-level puzzles every day until the exam, one floor type and one seating type.
• Read solving puzzles faster for the clue-ordering habit.