LET cheat sheet

Percentage relations: Part = Rate × Base; Rate = Part ÷ Base; Base = Part ÷ Rate - identify which of the three quantities is missing before computing.

Average speed = total distance ÷ total time; for equal distances covered at speeds a and b, average speed = 2ab ÷ (a + b), not (a + b) ÷ 2.

Simple interest I = Prt; compound amount A = P(1 + r/n)^(nt), where n is the number of compounding periods per year and r is the decimal rate.

Right-triangle and circle formulas: a² + b² = c²; area of a triangle = ½bh; circle area = πr² and circumference = 2πr.

Subject–verb agreement: two subjects joined by 'and' take a plural verb; 'each,' 'every,' 'either,' and 'neither' as subject heads take singular verbs.

Photosynthesis: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂; light reactions occur in the thylakoid membranes and the Calvin cycle in the stroma.

Base pairing: A–T and G–C in DNA; uracil replaces thymine in RNA; transcription happens in the nucleus and translation on the ribosome.

Philippine history anchors: independence proclaimed 12 June 1898 at Kawit; 1935 Commonwealth; the 1987 Constitution was ratified in a plebiscite on 2 February 1987.

Figures of speech: simile uses 'like' or 'as'; metaphor asserts identity without those words; personification gives human traits to non-human things; hyperbole is deliberate exaggeration.

RA 7836 (1994), the Philippine Teachers Professionalization Act, governs teacher licensure and created the Board for Professional Teachers under PRC supervision.

RA 4670 (1966), the Magna Carta for Public School Teachers, limits actual classroom teaching to six hours a day and provides salary scale, study leave, and tenure protection.

The Code of Ethics for Professional Teachers is Board Resolution No. 435, s. 1997, covering conduct toward the state, community, profession, and learners.

PPST (DepEd Order No. 42, s. 2017) has four career stages - Beginning, Proficient, Highly Proficient, Distinguished - organized into 7 domains and 37 strands.

Piaget's stages: sensorimotor (0–2), preoperational (2–7), concrete operational (7–11), formal operational (11 and above); tasks should match the learner's stage.

Bloom's revised taxonomy runs Remember → Understand → Apply → Analyze → Evaluate → Create; the verb in an objective signals the intended cognitive level.

Item difficulty P = (number correct) ÷ (number of examinees); P between 0.26 and 0.75 is generally acceptable for classroom tests.

Item discrimination D = (correct in upper group − correct in lower group) ÷ group size; a negative D means the item favors low scorers and needs revision.

Assessment decision rules: formative = during instruction and ungraded; summative = end of unit and graded; criterion-referenced = judged against a standard; norm-referenced = judged against peers.

Quadratic roots: x = [−b ± √(b² − 4ac)] ÷ 2a; discriminant > 0 gives two real roots, = 0 gives one real root, < 0 gives no real roots.

Slope m = (y₂ − y₁) ÷ (x₂ − x₁); parallel lines have equal slopes, perpendicular lines have negative-reciprocal slopes, and vertical lines have undefined slope.

Newton's laws: F = ma for net force; the first law states inertia; action–reaction pairs act on different bodies, so they never cancel each other.

Electricity: V = IR (Ohm's law); P = VI = I²R = V²/R; resistances add in series, while parallel resistances satisfy 1/R = 1/R₁ + 1/R₂.

Acids and bases: pH = −log[H⁺]; pH below 7 is acidic, 7 is neutral, above 7 is basic, and each unit is a tenfold change in hydrogen-ion concentration.

Organelle functions: mitochondria produce ATP by aerobic respiration; ribosomes synthesize protein; chloroplasts carry out photosynthesis; the Golgi apparatus packages and secretes.

Single-best-answer rule: the key must follow from the stated conditions alone; if two options are both true or are synonyms, neither can be the key.

Absolute qualifiers such as 'always,' 'never,' and 'all' are correct only when the underlying law admits no exception, as in the cell-theory claim that all cells come from pre-existing cells.