BD Police ASI Written cheat sheet

বাংলা বর্ণমালায় মোট ৫০টি বর্ণ: স্বরবর্ণ ১১টি (অ, আ, ই, ঈ, উ, ঊ, ঋ, এ, ঐ, ও, ঔ) এবং ব্যঞ্জনবর্ণ ৩৯টি।

ব্যঞ্জনবর্ণের মধ্যে অন্তঃস্থ/অর্ধস্বর ৪টি (য, র, ল, ব), উষ্ম ৪টি (শ, ষ, স, হ), এবং 'ৎ' ও 'ং' 'ঃ' যুক্তবর্ণ হিসেবে গণ্য।

স্বরবর্ণের সংক্ষিপ্ত রূপকে কার চিহ্ন বলে: আ=া, ই=ি, ঈ=ী, উ=ু, ঊ=ূ, ঋ=ৃ, এ=ে, ঐ=ৈ, ও=ো, ঔ=ৌ।

বাংলা ভাষায় মাত্রা আছে এমন বর্ণ ৩২টি; 'অ' ও 'আ'-এর মাত্রা নেই বলে এদের মাত্রাহীন বর্ণ বলা হয়।

সন্ধি প্রধানত তিন প্রকার: স্বরসন্ধি, ব্যঞ্জনসন্ধি ও বিসর্গসন্ধি; যেমন বিদ্যা+আলয়=বিদ্যালয় (স্বরসন্ধি)।

সমাসের প্রধান ভেদ: দ্বন্দ্ব, কর্মধারয়, তৎপুরুষ, বহুব্রীহি, দ্বিগু ও অব্যয়ীভাব - মোট ছয় প্রকার।

বাংলা সাহিত্যের আদি নিদর্শন 'চর্যাপদ' (আনুমানিক ৯৫০–১২০০ খ্রিস্টাব্দ), হরপ্রসাদ শাস্ত্রী ১৯০৭ সালে নেপালে এটি আবিষ্কার করেন।

মাইকেল মধুসূদন দত্ত বাংলা সাহিত্যে সনেট ও অমিত্রাক্ষর ছন্দের প্রবর্তক; তাঁর গ্রন্থ 'মেঘনাদবধ কাব্য' ও 'কপোতাক্ষ নদ' কবিতা উল্লেখযোগ্য।

রবীন্দ্রনাথ ঠাকুর ১৯১৩ সালে 'গীতাঞ্জলি'র ইংরেজি অনুবাদের জন্য সাহিত্যে নোবেল পুরস্কার পান; তিনিই প্রথম এশীয় নোবেল বিজয়ী।

Parts of speech are eight: noun, pronoun, verb, adjective, adverb, preposition, conjunction and interjection.

A gerund is a verb form ending in -ing that functions as a noun, e.g. 'Swimming is good exercise'; a participle modifies a noun, e.g. 'a running tap'.

Voice: active 'Rahim writes a letter' becomes passive 'A letter is written by Rahim' - object moves to subject position and the verb takes be + past participle.

Reported speech shifts tense back one step: present simple becomes past simple, present continuous becomes past continuous, and 'will' becomes 'would'.

Conditional sentences: Type 1 if + present simple, main clause will + verb; Type 2 if + past simple, main clause would + verb; Type 3 if + past perfect, main clause would have + past participle.

Common prepositions of time: 'in' for months, years and long periods; 'on' for days and dates; 'at' for exact times and night.

William Shakespeare wrote 37 plays, 154 sonnets and several narrative poems; 'Hamlet', 'Macbeth', 'Othello' and 'King Lear' are his four great tragedies.

John Milton's 'Paradise Lost' is an epic in blank verse, first published in ten books in 1667 and reorganised into twelve books in 1674.

Literary devices: simile uses like/as for comparison, metaphor states one thing is another, personification gives human qualities to non-human things, and alliteration repeats initial consonant sounds.

Percentage change = (new value − old value) ÷ old value × 100; a 20% increase followed by a 20% decrease gives a net 4% decrease.

Simple interest SI = P × r × t ÷ 100; compound amount A = P(1 + r/100)^t, where r is the annual rate and t is in years.

Profit percent = profit ÷ cost price × 100; selling price = cost price × (100 + profit%) ÷ 100.

Average speed for equal distances at speeds a and b is 2ab ÷ (a + b), not the arithmetic mean (a + b) ÷ 2.

Area formulas: rectangle l×b, triangle ½×base×height, circle πr², trapezium ½(a+b)h; circumference of a circle = 2πr.

Pythagoras' theorem: in a right triangle, hypotenuse² = base² + perpendicular²; the 3-4-5 and 5-12-13 triples are common right-triangle sets.

LCM × HCF of two positive integers equals the product of the two numbers; use prime factorisation to find either.

Sum of the first n natural numbers = n(n+1)/2; sum of squares = n(n+1)(2n+1)/6; sum of cubes = [n(n+1)/2]².

Work rate: if A finishes a job in x days and B in y days, together they finish it in xy ÷ (x + y) days.

Bangladesh gained independence on 26 March 1971 and Victory Day is 16 December 1971; the national anthem 'Amar Shonar Bangla' was written by Rabindranath Tagore.

The Constitution of Bangladesh was adopted on 4 November 1972 and came into effect on 16 December 1972; it originally had 153 articles in 11 parts.

Bangladesh's national flower is the water lily (shapla), national fruit jackfruit, national bird the oriental magpie-robin (doyel), and national animal the Bengal tiger.

The Padma Bridge, opened in June 2022, is Bangladesh's longest bridge; the Bangabandhu Sheikh Mujibur Rahman Tunnel under the Karnaphuli is the country's first underwater tunnel.

The United Nations was founded on 24 October 1945 and has 193 member states; its principal organs include the General Assembly, Security Council and ICJ at The Hague.

The Security Council has 15 members: five permanent (China, France, Russia, UK, USA) with veto power and ten elected for two-year terms.

SAARC was founded in 1985 with headquarters in Kathmandu; ASEAN was founded in 1967 with headquarters in Jakarta.

The Nobel Prize is awarded in six categories; the Peace Prize is announced in Oslo, Norway, while the others are awarded in Stockholm, Sweden.

Bangladesh shares borders with India and Myanmar, and its southern boundary is the Bay of Bengal; the Sundarbans is the world's largest mangrove forest.

1 byte = 8 bits; 1 kilobyte = 1024 bytes, 1 megabyte = 1024 KB, 1 gigabyte = 1024 MB, 1 terabyte = 1024 GB.

RAM is volatile working memory that loses data on power off; ROM is non-volatile and stores firmware such as the BIOS.

Input devices: keyboard, mouse, scanner, microphone, joystick; output devices: monitor, printer, speaker, plotter.

The CPU has three main parts - arithmetic logic unit (ALU), control unit and registers - and executes the fetch-decode-execute cycle.

Operating systems include Windows, Linux, macOS and Android; MS-DOS was a single-user command-line OS.

Shortcuts: Ctrl+C copy, Ctrl+V paste, Ctrl+X cut, Ctrl+Z undo, Ctrl+S save, Ctrl+P print, Ctrl+A select all.

A URL has the form protocol://domain/path; HTTP is the web transfer protocol and HTTPS adds encryption via TLS.

IPv4 addresses are 32-bit (four octets, 0–255 each) while IPv6 addresses are 128-bit.

Malware types include virus (attaches to files), worm (self-replicates across networks) and Trojan (disguised as legitimate software).

Newton's three laws: inertia unless a net force acts; F = ma; every action has an equal and opposite reaction.

Speed = distance ÷ time; acceleration = change in velocity ÷ time; the SI unit of force is the newton (kg·m/s²).

Work = force × displacement in the direction of force; power = work ÷ time, measured in watts; energy is measured in joules.

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

Light travels at about 3 × 10⁸ m/s in vacuum; reflection angle equals incidence angle, and refraction bends light toward the normal when entering a denser medium.

The pH scale runs 0–14: below 7 acidic, 7 neutral, above 7 basic; pH = −log₁₀[H⁺].

An acid turns blue litmus red and reacts with a base to give salt and water (neutralisation); a base turns red litmus blue.

Atomic number = number of protons; mass number = protons + neutrons; isotopes have the same protons but different neutrons.

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

Earth's layers: crust, mantle, outer core and inner core; the crust is thinnest under oceans and thickest under mountains.

Latitude lines run east–west and measure distance north or south of the equator (0°); longitude lines run north–south and measure east or west of the prime meridian (0°).

The Tropic of Cancer is at 23.5°N and the Tropic of Capricorn at 23.5°S; the Arctic Circle is 66.5°N and the Antarctic Circle 66.5°S.

Earth rotates on its axis once in about 24 hours causing day and night, and revolves around the Sun in about 365.25 days causing seasons.

The atmosphere has layers: troposphere (weather occurs), stratosphere (ozone layer), mesosphere, thermosphere and exosphere.

Bangladesh lies between roughly 20°34′N and 26°38′N latitude and 88°01′E and 92°41′E longitude, with an area of about 147,570 km².

The Ganges (Padma), Brahmaputra (Jamuna) and Meghna form the world's largest delta system in Bangladesh.

Rivers: the Amazon carries the largest volume of water, the Nile is traditionally the longest, and the Dead Sea is the lowest land point on Earth.

Climate types: tropical monsoon in Bangladesh with hot, rainy and cool seasons; deserts form near 30° latitude due to descending dry air.

Greenhouse gases include CO₂, methane, nitrous oxide and water vapour; CO₂ is the largest contributor from fossil fuel burning.

Global warming of about 1.1–1.2°C above pre-industrial levels has occurred; the Paris Agreement aims to keep warming well below 2°C and pursue 1.5°C.

Ozone depletion is caused mainly by chlorofluorocarbons (CFCs); the Montreal Protocol (1987) phases out ozone-depleting substances.

Acid rain forms when SO₂ and NOₓ react with water vapour to make sulphuric and nitric acids; it damages soils, lakes and buildings.

Bangladesh's disaster risks include cyclones from the Bay of Bengal, river floods, riverbank erosion, tornadoes, droughts and landslides in the Chittagong Hill Tracts.

The cyclone warning system uses signal numbers 1–10; signal 10 is the highest and indicates a severe cyclone with wind speeds above 88 km/h.

The Bangladesh Meteorological Department issues weather forecasts, and the Flood Forecasting and Warning Centre monitors river levels.

The Sendai Framework (2015–2030) sets four priorities for disaster risk reduction, including understanding risk and strengthening governance.

Ecosystem services include provisioning (food, water), regulating (climate, flood control), cultural and supporting services; mangrove forests reduce cyclone surge damage.