BOB LBO cheat sheet

Syllogism: two negative premises yield no valid conclusion; two particular premises yield no valid conclusion.

Venn-diagram method: draw the smallest region consistent with each premise, then test whether the conclusion holds in every consistent diagram.

Blood relations: convert each statement into a signed relation (+male/−female for gender, generation offsets for age) before solving chains.

Direction sense: track net displacement as (x, y) coordinates; final distance = √(x² + y²), direction from the quadrant of the resultant.

Seating arrangement: fix the single most constrained person first, then place others by relative position; circular facing-centre means left is clockwise.

Coding-decoding: test letter-shift (positional ±k), reversal, and alphabet-pair (A↔Z) rules in that order before assuming arbitrary mapping.

Ordering/ranking: if A is nth from the top and mth from the bottom, total = n + m − 1.

Series completion: check successive differences, then ratios, then alternating sub-series at odd and even positions.

Statement-assumption: an assumption is valid only if negating it destroys the argument; reject restatements of the statement itself.

Simple interest: SI = P·R·T/100; compound interest: A = P(1 + R/100)^T, CI = A − P.

Effective annual rate for compounding n times a year: (1 + r/n)^n − 1; doubling under CI at rate r takes ≈ 72/r years.

Profit and loss: profit% is computed on cost price unless stated; successive discounts d1, d2 give net price factor (1 − d1)(1 − d2).

Speed: distance = speed × time; for a train of length L crossing a platform of length P, time = (L + P)/speed.

Boats: downstream speed = b + s, upstream = b − s; time ratio upstream:downstream = (b + s):(b − s).

Mixtures: replacement rule - final pure quantity = initial × (1 − replaced/total)^n.

Permutations and combinations: nPr = n!/(n − r)!, nCr = n!/(r!(n − r)!); arrangements of a word with repeats = n!/(p!q!…).

Probability: P(A∪B) = P(A) + P(B) − P(A∩B); independent events multiply, mutually exclusive events add.

Work: combined rate = 1/a + 1/b; if A is k times as efficient as B, time ratio A:B = 1:k.

Subject-verb agreement: 'one of the + plural noun' takes a singular verb; 'each, every, either, neither' take singular verbs.

Collective nouns (team, jury, committee) take a singular verb when acting as a unit and a plural verb when members act individually.

Conditional structures: Type 1 if + present, will + base; Type 2 if + past, would + base; Type 3 if + past perfect, would have + past participle.

Reported speech shifts tense one step back (present→past, past→past perfect) and changes time/place words (now→then, here→there).

Passive voice: object becomes subject, verb becomes be + past participle, and the original subject moves to a by-phrase or is dropped.

Prepositions of time: in for months/years, on for days/dates, at for clock times; since with a point, for with a duration.

Cloze and error-spotting: test each option for collocation and parallelism before judging grammaticality in isolation.

Reading comprehension: locate the claim in the passage first, then eliminate options that overstate, invert, or add unstated scope.

Indian polity: Fundamental Rights sit in Part III (Articles 12–35); Directive Principles in Part IV (Articles 36–51).

The President is elected by an electoral college of elected MPs and elected MLAs; the Vice-President by both Houses of Parliament only.

RBI was established on 1 April 1935 under the RBI Act 1934 and nationalised in 1949; it issues currency notes except the one-rupee note.

Indian economy: repo rate is the rate at which RBI lends to banks; reverse repo absorbs liquidity; CRR and SLR are reserve requirements.

Geography: the Tropic of Cancer passes through eight Indian states, and the Standard Meridian of India is 82°30′E.

Static science: the SI unit of force is the newton, of pressure the pascal, and of power the watt.

Awards and institutions: the Nobel Memorial Prize in Economics is not one of the original Nobel Prizes; it was added in 1968.

Dates to anchor: UN founded 24 October 1945; World Bank and IMF established at Bretton Woods in 1944, operating from 1946.

NEFT settles in batches (half-hourly, 24×7), RTGS is real-time with a minimum of ₹2 lakh, and IMPS runs 24×7 through NPCI.

UPI is built on the IMPS rail and operated by NPCI; a UPI ID (VPA) maps to an account without exposing the account number.

Banking types: savings and current deposits are demand liabilities; fixed and recurring deposits are time liabilities.

Cheque crossing (general or special) restricts payment to a bank; a bearer cheque is payable to whoever presents it.

Computer basics: 1 byte = 8 bits; 1 KB = 1024 bytes; ROM is non-volatile, RAM is volatile and loses contents on power-off.

OSI model has seven layers; TCP operates at the transport layer, IP at the network layer, and HTTP at the application layer.

IPv4 uses 32-bit addresses, IPv6 uses 128-bit; DNS resolves domain names to IP addresses.

Security: phishing is deceptive credential capture, while a Trojan is malware disguised as legitimate software; a firewall filters traffic by rule set.

Keyboard shortcuts: Ctrl+C copy, Ctrl+V paste, Ctrl+Z undo, Ctrl+F find; F5 refreshes in most browsers.