General Science & Environment
pH Memory Trick — Acids are pH 0-7 (think "A" comes before "7"), bases 7-14. Pure water = 7. Lemon ~2, blood ~7.4, bleach ~13. Remember: lower number = stronger acid.
Vitamin Deficiency Chain — A-Night, B1-Beri, C-Scurvy, D-Bone, K-Klot. A for night blindness, B1 for beriberi, C for scurvy, D for bone issues (rickets), K for blood clotting.
Planet Order — My Very Educated Mother Just Served Us Nachos (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune). For size order: Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury.
Reactivity Series Top-5 — Please Stop Calling Me A (Potassium, Sodium, Calcium, Magnesium, Aluminium) — most reactive metals, displace hydrogen from water/acids easily.
Biology
Mitosis Phases — PMAT: Prophase, Metaphase, Anaphase, Telophase. Chromosomes appear, align at center, are pulled apart, then two nuclei form. Meiosis does PMAT twice.
Blood Group Compatibility — O is donor, AB is acceptor. O-negative = universal donor (gives to all), AB-positive = universal recipient (takes from all). Remember: O has nothing to give antibodies to.
Cranial Nerve Count — Humans have exactly 12 pairs of cranial nerves. Mnemonic for names: On Old Olympus Towering Tops (Olfactory, Optic, Oculomotor, Trochlear, Trigeminal...).
Chemistry
BODMAS Trap in Chemical Equations — Balance atoms not coefficients first. In redox: OIL RIG (Oxidation Is Loss, Reduction Is Gain of electrons). LEO goes GER also works (Lose Electrons Oxidation, Gain Electrons Reduction).
Periodic Table Groups — Group 1: Alkali metals (Li, Na, K, Rb, Cs, Fr). Group 17: Halogens (F, Cl, Br, I, At). Group 18: Noble gases (He, Ne, Ar, Kr, Xe, Rn). Remember positions for exam MCQs.
Electrolysis Memory — PANCHO: Positive Anode Negative Cathode (Oxidation at anode, reduction at cathode). Anions move to anode, cations to cathode—opposites attract.
Arithmetic
Divisibility by 11 — Subtract alternating digits. If result is 0 or 11 multiple, number divides by 11. Example: 121 → 1-2+1=0, divisible. For 1331 → 1-3+3-1=0, divisible.
Percentage-Fraction快速 Conversions — 12.5%=1/8, 16.67%=1/6, 20%=1/5, 25%=1/4, 33.33%=1/3, 50%=1/2, 66.67%=2/3, 75%=3/4. Memorize these nine for instant calculation.
Compound Interest Shortcut — For 2 years: CI-SI difference = P(R/100)². If SI=1000 and R=10%, extra CI = 1000×(10/100)² = ₹10. Works only for 2-year problems.