TNPSC · Subject-wise preparation

TNPSC aptitude and mental ability: topics, formulas, worked examples

By the PrepMatic team · Updated 8 Oct 2026 · 9 min read

TNPSC Aptitude and Mental Ability is Part C of the Group 4 paper: 25 questions at SSLC standard, made up of 15 aptitude questions and 10 reasoning questions (the unit split is indicative, as TNPSC calls it). At 1.5 marks a question, the section is worth 37.5 of the 300 marks. The official topic list is short and the maths is Class 10 level and below, so this is one of the easiest sections to improve with practice. The same 25-question part appears in the Group 2 and 2A prelims.

What the official syllabus lists

The Group 4 notification (syllabus code 496) gives these topics for Part C.

Notice what is not listed: speed and distance, profit and loss, averages and ages. They are not named in the notification, so do not spend your first month on them. Percentage and ratio will cover most of the thinking those chapters need. Use Group 4 syllabus to see how Part C sits with the other two parts, and the exam pattern for marks and timing.

Where else does it appear? Group 2 and 2A prelims have a 25-question Aptitude and Mental Ability part at SSLC standard, and the Group 1 prelims paper carries 25 aptitude questions as well. The Group 2A mains has a separate, longer reasoning part, which you can read about in the Group 2 syllabus.

Why it deserves steady practice

The qualifying rules in the Group 4 notification are an overall minimum of 90 out of 300 and a 40% gate on the Tamil Part A (explained in the marking scheme). Part C marks count towards both your total and your rank. A section with 25 answerable questions and a fixed set of topics is where practice converts to marks most reliably. Unlike General Studies, you do not need to remember new facts: you need method and speed.

Formula sheet

Use π = 22/7 when the radius is a multiple of 7, and 3.14 otherwise, unless the question says what to use.

Worked examples

Every answer here is easy to verify, so try each one first without looking.

1. Simplification. Evaluate (36 × 25 − 400) ÷ 50 + 12. Work inside the bracket: 900 − 400 = 500. Then 500 ÷ 50 = 10, and 10 + 12 = 22.

2. Percentage. A shirt priced at ₹500 is marked up by 20% and then discounted by 20%. After the rise the price is 500 × 1.2 = ₹600; after the fall it is 600 × 0.8 = ₹480. The net change is a 4% fall, which matches the a²/100 rule (20²/100 = 4).

3. LCM. Three bells ring every 12, 18 and 30 minutes and ring together at 9:00 AM. When do they next ring together? LCM(12, 18, 30) = 180 minutes, so the next time is 12:00 noon (3 hours later).

4. HCF. Find the largest tile that exactly fits both sides of a floor 84 cm by 126 cm. HCF(84, 126) = 42 cm, and the matching LCM is 84 × 126 ÷ 42 = 252.

5. Ratio. Share ₹1,800 in the ratio 2:3:4. Total parts = 9, so one part is ₹200 and the shares are ₹400, ₹600 and ₹800.

6. Simple and compound interest. On ₹10,000 at 10% per year for 2 years, SI = 10,000 × 10 × 2 / 100 = ₹2,000. The compound amount is 10,000 × (1.1)² = ₹12,100, so CI = ₹2,100. The difference of ₹100 equals P(r/100)² = 10,000 × 0.01, a shortcut for "difference between CI and SI for 2 years".

7. Volume. A rectangular tank is 5 m × 4 m × 3 m. Its volume is 60 m³, and since 1 m³ = 1,000 litres, it holds 60,000 litres.

8. Time and work. A can finish a job in 10 days and B in 15 days. Together their daily work is 1/10 + 1/15 = 5/30 = 1/6, so they take 6 days. The same answer comes from ab/(a+b) = 150/25 = 6.

Reasoning: how to approach each type

• Number series. Look first at the differences. In 2, 6, 12, 20, 30 the differences are 4, 6, 8, 10, so the next difference is 12 and the next term is 42. If differences don't settle, test ratios (3, 6, 12, 24 gives 48) and squares (1, 4, 9, 16, 25 gives 36).
• Alpha-numeric reasoning. Write A = 1 to Z = 26 along the top of your rough sheet. The position of a letter from the right is 27 minus its position from the left, so K is the 11th from the left and the 16th from the right. For a letter series such as A, C, F, J, O the gaps are +2, +3, +4, +5, so the next letter is O + 6, which is U. As a coding check, T + N + P + S + C = 20 + 14 + 16 + 19 + 3 = 72.
• Dice. On a standard die the opposite faces add up to 7 (1 opposite 6, 2 opposite 5, 3 opposite 4). If a die is shown twice and two faces are common, the other two visible faces are opposite each other. Example: shown as (1, 2, 3) and (1, 3, 5), then 2 is opposite 5. Always use the picture in the question if it breaks the standard rule.
• Logical reasoning. For blood-relation items, draw the family tree. "She is the daughter of my grandfather's only son" means the speaker's father's daughter, so she is the speaker's sister. For direction items, draw a small map: 5 km east, 3 km north and 5 km west leaves you 3 km north of the start.
• Puzzles. Make a small grid, fill in what is certain first, and do not guess before the facts run out.
• Visual reasoning. Look for what changes from figure to figure: rotation, count of parts, shading, position. Test one change at a time.

Speed tips

1. Learn tables to 20, squares to 25 and cubes to 10. They make simplification and percentage much faster.
2. Memorise fraction-percent pairs: 1/2 = 50%, 1/3 = 33.3%, 1/4 = 25%, 1/5 = 20%, 1/6 = 16.7%, 1/7 = 14.3%, 1/8 = 12.5%, 1/9 = 11.1%, 1/10 = 10%.
3. Use the options. In the multiple-choice format, you can often eliminate two options by estimating before you calculate.
4. Skip and return. A question that needs more than about 90 seconds can wait. Mark it and move on.
5. Check units. Time and work and volume questions often hide a conversion, such as minutes against hours or cm against m.

TNPSC's marking, as described in the Group 4 notification, deducts nothing for a wrong answer but deducts 0.5 mark for a question left blank. That matters here, because aptitude is where you are most tempted to skip a long question. The marking scheme page explains the rule and the OMR option [E].

A practice routine

• Weeks 1 to 4 (learning): one topic every two or three days. Read the Samacheer Kalvi Class 6 to 10 maths chapter, copy the formulas, do 20 problems.
• Weeks 5 to 8 (speed): 15 minutes a day of mixed arithmetic, timed. Add 10 reasoning questions each day.
• From then on: a timed 25-question set every second day, and one section within each full mock. Keep a log of the topic where each mistake occurred; most aspirants find the same three or four topics recurring.

A reasonable target for the exam is about 30 minutes for all 25 questions. Rehearse that in your mocks so that it is a habit and not a hope. The general approach to mock scheduling is in the mock tests guide.

Practising with PrepMatic

PrepMatic's free assessment shows how you do in Aptitude compared with your other subjects, so you can decide how much of your plan this section needs. You can then build a custom mock restricted to the subject you choose, with your own number of questions, duration and difficulty, or take a topic test of about 15 questions in 30 minutes. The analytics show subject-wise accuracy and speed per question, which tells you whether your problem is knowledge or time. Questions are AI-generated, so cross-check any answer that surprises you against your textbook method.

Frequently asked questions

How many aptitude questions are there in TNPSC Group 4?

Part C has 25 questions: 15 in Aptitude and 10 in Reasoning, according to the Group 4 notification. TNPSC states that such unit-wise counts are only indicative.

What is the standard of the aptitude section?

SSLC standard, which means Class 10 maths and below. You do not need formulas from higher classes for the topics listed in the notification.

How much time should I spend on the aptitude section?

The Group 4 paper is a single 3-hour paper with 200 questions and no separate timing for each part, so you decide. About 30 minutes for the 25 aptitude and reasoning questions is a sensible planning figure; practise it in mocks and adjust.

Are profit and loss, speed and distance in the TNPSC syllabus?

They are not named in the Part C topic list of the Group 4 notification. Some questions may overlap with percentage and ratio, so learn those well and treat the unlisted chapters as low priority.

Is the Group 2 aptitude section harder?

The Group 2 and 2A prelims also use SSLC standard for Part C, with 25 questions, so the prelims level is similar. The Group 2A mains has a longer reasoning part, which the Group 2 guides cover.

Official sources

• Group 4 Notification No. 11/2026, Annexure III (syllabus code 496): Part C topics, marks and OMR rules.
• Group 2 and 2A Notification No. 11/2025: the prelims scheme with Part C.
• Tamil Nadu School Education textbooks: Samacheer Kalvi maths books for Classes 6 to 10.

Confirm topics, question counts and rules in the latest TNPSC notification before you plan. The TNPSC hub links to every exam and subject guide.

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