CDS (Combined Defence Services) Exam
Why This Chapter Matters
CDS is conducted by UPSC twice a year for entry into Indian Army, Navy, and Air Force. Three papers: English (100 marks), General Knowledge (100 marks), Elementary Mathematics (100 marks). This guide covers the pattern and key content.
CDS Exam Structure
For IMA, INA, AFA:
For OTA (Officers Training Academy):
Negative marking: 1/3 mark deducted for wrong answer.
Paper 1 — English
Key Grammar Topics
Same as NDA English but at a slightly higher level.
Spotting Errors: Read the sentence, identify which underlined part has grammatical error.
Sentence Arrangement (Para Jumbles): Rearrange sentences to form coherent paragraph. Find opener (no pronoun dependency), use connectors (however, therefore, moreover) as clues.
Fill in the Blanks: Vocabulary + grammar. Context determines the correct word.
Comprehension Passages: 4-5 questions per passage. Main idea, inference, vocabulary.
Ordering of Words: Arrange jumbled words to make correct sentence.
Synonyms and Antonyms: High-frequency vocabulary from previous years.
Important Vocabulary for CDS
Formal/Legal vocabulary: Abate, Abrogate, Adjudicate, Acquiesce, Ameliorate, Amicable, Approbation, Auspicious
Military vocabulary: Sortie, Reconnaissance, Debriefing, Deployment, Echelon, Flank, Ordnance, Salvo
Paper 2 — General Knowledge
Indian and World History
Key focus for CDS: Modern India (British era to Independence) and Post-Independence India
Post-independence India:
First President: Dr. Rajendra Prasad
First PM: Pandit Jawaharlal Nehru
First General Election: 1952
Republic Day: 26 January 1950 (Constitution came into force)
Wars fought by India:
1947-48: First Kashmir War
1962: Sino-Indian War (China attacked)
1965: Indo-Pakistan War
1971: Bangladesh Liberation War (creation of Bangladesh, Shimla Agreement 1972)
1999: Kargil War (Pakistan-backed infiltration, Operation Vijay)
Indian Constitution and Polity
Key facts:
Constitution drafted by: Constituent Assembly chaired by Dr. B.R. Ambedkar (drafting committee chairman)
Constitution adopted: 26 November 1949 | Came into force: 26 January 1950
Total articles: 448 (originally 395), 12 schedules, 104 amendments (as of 2023)
Longest constitution in the world.
Fundamental Rights (Part III, Articles 12-35):
Directive Principles (Part IV): Non-justiciable but fundamental to governance.
Fundamental Duties (Part IVA, Art 51A): Added by 42nd Amendment.
Parliament:
Rajya Sabha: Upper house, 250 members max (238 elected + 12 nominated), 6-year terms
Lok Sabha: Lower house, 552 members max, 5-year term
Money Bill: originates only in Lok Sabha
Emergency provisions: National Emergency (Art 352), State Emergency/President's Rule (Art 356), Financial Emergency (Art 360)
Science and Technology
Space technology:
ISRO founded: 1969 | Chairman: S. Somnath (current)
Key missions: Chandrayaan-1(2008), Chandrayaan-2(2019), Chandrayaan-3(2023, successful south pole landing), Mangalyaan/Mars Orbiter(2013-2022), Gaganyaan (upcoming human spaceflight)
Nuclear technology:
India's nuclear doctrine: No First Use (NFU) policy
Nuclear power plants: Tarapur (1st), Kudankulam (largest), Kaiga, Rawatbhata
Defence technology:
DRDO: Defence Research and Development Organisation
Missiles: Agni (ICBM), Prithvi (short-range), BrahMos (supersonic cruise), Astra (air-to-air), Akash (surface-to-air)
Fighter jets: HAL Tejas (indigenous), Rafale (from France), Sukhoi-30
Naval: INS Vikrant (1st indigenous aircraft carrier, commissioned 2022), INS Vikramaditya
Paper 3 — Elementary Mathematics
Key Topics
Number System: HCF, LCM, divisibility rules, fractions, decimals
Algebra: Equations (linear, quadratic), polynomials, progressions
Trigonometry: Ratios, identities, heights and distances
Geometry: Triangles, circles, polygons, 3D shapes
Mensuration: Area, perimeter, volume of all standard shapes
Statistics: Mean, median, mode, range
Data Interpretation: Tables, bar graphs, pie charts
High-Yield Topics for CDS Maths
Mensuration formulas:
Cylinder: CSA=2πrh, Volume=πr^2h
Cone: CSA=πrl (l=slant height), Volume=(1/3)πr^2h
Sphere: TSA=4πr^2, Volume=(4/3)πr^3
Frustum: Volume=(πh/3)(R^2+r^2+Rr)
Time and Work:
If A takes a days and B takes b days: Together = ab/(a+b) days
Simple and Compound Interest:
SI = PRT/100 | CI: A = P(1+R/100)^T | CI-SI = P(R/100)^2 for 2 years
PYQs (CDS)
CDS 2023 (English): Arrange in correct sequence: P(The police) Q(have arrested) R(the thief) S(who had) T(stolen the car)
Correct: P-Q-R-S-T = "The police have arrested the thief who had stolen the car."
CDS 2022 (GK): Operation Vijay was conducted in:
Kargil (1999) — to evict Pakistani-backed intruders from Kargil heights.
CDS 2021 (Maths): A train 150m long passes a pole in 15 seconds. Its speed in km/h?
Speed = 150/15 = 10 m/s = 10 × 18/5 = 36 km/h.