BAF Officer Cadet cheat sheet

Subject-verb agreement: singular subject takes singular verb; compound subjects joined by 'and' take a plural verb unless they form one idea.

Tense sequence: a past main clause normally takes a past or past-perfect subordinate clause, not a present tense.

Active to passive: object becomes subject, verb becomes 'be + past participle', agent introduced by 'by'.

Direct to indirect speech: shift present to past, 'today' to 'that day', 'tomorrow' to 'the next day', and adjust pronouns to the reporter.

Articles: 'a/an' before singular countable nouns (an before vowel sounds), 'the' for specific or unique referents.

Preposition pairs to memorize: 'comprise' takes no 'of'; 'consist of'; 'differ from'; 'superior to'; 'comply with'.

Modals: 'should/would/could/might' in conditional clauses; 'will/would' never follow 'if' in the same clause.

Commonly confused: 'affect' (verb) vs 'effect' (noun); 'principal' (main) vs 'principle' (rule); 'lie' (recline) vs 'lay' (place).

Quadratic roots of ax²+bx+c=0: sum = -b/a, product = c/a; discriminant D=b²-4ac determines real/equal/complex roots.

Arithmetic progression: nth term a+(n-1)d; sum = n/2[2a+(n-1)d]. Geometric progression: nth term ar^(n-1); sum = a(rⁿ-1)/(r-1).

Area of triangle: ½×base×height or √(s(s-a)(s-b)(s-c)) with s = semiperimeter.

Circle: area = πr², circumference = 2πr; arc length = (θ/360)×2πr for central angle θ in degrees.

Trigonometric identities: sin²θ+cos²θ=1; 1+tan²θ=sec²θ; sin2θ=2sinθcosθ.

Logarithm rules: log(mn)=log m+log n; log(m/n)=log m−log n; log(mⁿ)=n log m; log_b b=1.

Permutation vs combination: nPr = n!/(n−r)! (order matters); nCr = n!/[r!(n−r)!] (order does not matter).

Simple interest = PTR/100; compound amount = P(1+R/100)^T; average = sum of terms ÷ number of terms.

Newton's second law: F = ma; weight W = mg with g ≈ 9.8 m/s² near Earth's surface.

Equations of motion (uniform acceleration): v = u+at; s = ut+½at²; v² = u²+2as.

Kinetic energy = ½mv²; potential energy = mgh; work = force × displacement × cosθ; power = work/time.

Ohm's law: V = IR; power P = VI = I²R = V²/R; resistors in series add, in parallel reciprocals add.

Wave relation: speed = frequency × wavelength (v = fλ); sound travels faster in solids than in gases.

Density = mass/volume; pressure = force/area; pressure in liquid = hρg.

Law of reflection: angle of incidence equals angle of reflection; light bends toward the normal entering a denser medium.

Heat: Q = mcΔT for temperature change; latent heat Q = mL at phase change; efficiency = useful output ÷ total input × 100%.

United Nations founded 1945; headquarters in New York; Security Council has five permanent veto members: USA, UK, France, Russia, China.

SAARC founded 1985 with secretariat in Kathmandu; ASEAN founded 1967 with secretariat in Jakarta.

Nobel Prizes are awarded annually in Physics, Chemistry, Medicine, Literature, Peace, and Economic Sciences.

Olympic Games are held every four years; the Summer and Winter Games alternate on a four-year cycle.

Bangladesh joined the United Nations in 1974 and is a major troop contributor to UN peacekeeping.

BRICS grouping originally comprised Brazil, Russia, India, China, South Africa; expansion adds members such as Egypt and Ethiopia.

World Health Organization and UNESCO are UN specialized agencies; IMF and World Bank are Bretton Woods institutions based in Washington.

Greenhouse gases chiefly include CO₂, methane, and nitrous oxide; the Paris Agreement targets limiting warming well below 2°C.

Language Movement peaked on 21 February 1952 when students in Dhaka were killed; UNESCO declared that date International Mother Language Day.

Sheikh Mujibur Rahman delivered the 7 March 1971 speech at Ramna Race Course calling for independence struggle.

Operation Searchlight began on the night of 25 March 1971; independence was declared on 26 March 1971.

The Liberation War ended with the Pakistani surrender on 16 December 1971 at Dhaka; Bangladesh observes Victory Day then.

Bangladesh constitution was adopted on 4 November 1972 and took effect on 16 December 1972.

National symbols: national flower water lily, national bird oriental magpie-robin, national animal Bengal tiger, national fish hilsa.

Bangladesh has six administrative divisions historically; Mymensingh was added as a division in 2015.

The Padma Bridge, opened in 2022, is Bangladesh's longest bridge and was built without foreign donor financing.

Atomic number = number of protons; mass number = protons + neutrons; isotopes differ in neutrons only.

pH scale: below 7 acidic, 7 neutral, above 7 basic; pH = −log[H⁺].

Mole concept: one mole = 6.022×10²³ particles; moles = mass ÷ molar mass.

Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, occurring in chloroplasts using chlorophyll and light.

Human blood groups follow ABO and Rh systems; O-negative is the universal donor, AB-positive the universal recipient.

DNA is a double helix of nucleotides with bases adenine-thymine and guanine-cytosine; RNA replaces thymine with uracil.

Cell organelles: mitochondria for respiration energy, ribosomes for protein synthesis, nucleus holds genetic material.

Periodic trends: atomic radius decreases across a period and increases down a group; electronegativity increases across a period.

Number series: test differences, ratios, squares/cubes, and alternating patterns before assuming a rule.

Odd-one-out: classify items by a single shared attribute; the outlier breaks that attribute.

Coding-decoding: letter position A=1 to Z=26; reverse alphabet maps A↔Z, B↔Y, so position n maps to 27−n.

Blood relations: draw a family tree; 'brother of my father' = uncle, 'son of my brother' = nephew.

Direction sense: track net displacement with vectors; two perpendicular moves give resultant by Pythagoras.

Syllogism: a conclusion follows only if true in every possible diagram of the premises; 'some' statements are not reversible.

Analogy: identify the relation (part-whole, cause-effect, synonym) and apply the same relation to the target pair.

Seating arrangement: fix one anchor person, then place others clockwise/counterclockwise using stated left/right constraints.