Edutest cheat sheet

Percentage change = (new − old) ÷ old × 100; a 20% increase then 20% decrease gives net −4%, not 0%.

Ratio a:b:c splits a total T into parts a/(a+b+c)×T, b/(a+b+c)×T, c/(a+b+c)×T.

Average speed for equal distances = 2xy/(x+y), not (x+y)/2; for equal times, average = (x+y)/2.

Compound interest: A = P(1 + r/n)^(nt); simple interest: A = P(1 + rt).

Work rate: if A finishes in a days and B in b days, together they take ab/(a+b) days.

Number series: check differences, then ratios, then alternating patterns (every other term), then squares/cubes.

Direct proportion: y = kx; inverse proportion: y = k/x; find k from a known pair before solving.

Percentage of a percentage: a% of b% of N = (a/100)(b/100)N; e.g., 20% of 50% = 10%.

Analogies: determine the precise relationship (part:whole, cause:effect, synonym, antonym, degree) before choosing.

Odd-one-out: group words by shared meaning, word class, or category; the odd word lacks the shared property.

Letter series: convert letters to positions (A=1 … Z=26) and look for constant or increasing jumps.

Word codes: map each letter to its coded letter and identify the shift (e.g., +3) or reversal pattern.

Antonyms and synonyms: eliminate answer choices that are too broad, too narrow, or only loosely related.

Logical deduction: ‘all A are B’ does not imply ‘all B are A’; only valid conclusions follow necessarily.

Sentence completion: use the connector (but, because, although) to decide whether the missing word is similar or opposite.

Hidden words: scan for a smaller word embedded across a phrase without changing letter order.

Main idea = the point the whole passage supports; details support it but do not replace it.

Inference must be forced by the text; if an answer needs outside knowledge, it is not supported.

Tone words (critical, neutral, enthusiastic) are signaled by adjectives, adverbs, and punctuation.

‘According to the passage’ questions require locating explicit text, not personal opinion.

Author’s purpose (inform, persuade, entertain, compare) is identified from structure and verb choices.

Vocabulary in context: substitute each option into the sentence and check whether the passage meaning holds.

Passage structure: introduction, supporting evidence, counterargument, conclusion; note where each appears.

Eliminate extremes (all, never, always) unless the passage states them absolutely.

Area of a triangle = ½ × base × height; area of a circle = πr²; circumference = 2πr.

Pythagorean theorem: a² + b² = c² for right triangles; c is the hypotenuse.

Solve linear equations by performing the same operation on both sides until the variable is isolated.

Slope = (y₂ − y₁)/(x₂ − x₁); parallel lines have equal slopes; perpendicular slopes multiply to −1.

Quadratic formula: x = [−b ± √(b² − 4ac)]/(2a); discriminant b² − 4ac tells the number of real roots.

Volume of a cylinder = πr²h; volume of a cone = ⅓πr²h; volume of a sphere = (4/3)πr³.

Probability of an event = favorable outcomes ÷ total equally likely outcomes; P(not A) = 1 − P(A).

Mean = sum ÷ count; median = middle value when ordered; mode = most frequent value.

A complete sentence needs a subject and a finite verb; fragments and run-ons are the most common errors.

Comma splice: two independent clauses joined only by a comma; fix with a conjunction, semicolon, or period.

Subject–verb agreement: singular subject takes singular verb; ignore phrases between subject and verb.

Pronoun reference must be unambiguous; ‘it’ or ‘they’ must clearly point to one noun.

Parallel structure: items in a list or comparison must share the same grammatical form.

Modifiers should sit next to the word they describe; dangling modifiers lack a logical subject.

Punctuation: use a colon after a complete clause to introduce a list or explanation; use commas for nonessential clauses.

Formal writing avoids contractions, slang, and second person unless the prompt specifies otherwise.