SIMPLIFICATION (5-7 questions — easy, do first):
  BODMAS: Brackets, Of, Division, Multiplication, Addition, Subtraction
  Approximation: round to nearest 5 for multiple choice
  Fraction comparison: cross multiply or convert to decimal
  Square roots: learn perfect squares (1-50) for quick identification

NUMBER SYSTEM:
  Divisibility rules:
    2: last digit even | 3: sum of digits divisible by 3
    4: last two digits | 5: ends in 0 or 5 | 6: divisible by 2 and 3
    8: last three digits | 9: sum of digits divisible by 9 | 11: alternating sum
  HCF and LCM: HCF × LCM = product of two numbers
  Remainder theorem: for pattern questions

MENSURATION — IMPORTANT FORMULAS:
  Square: area=a², perimeter=4a
  Rectangle: area=l×b, perimeter=2(l+b), diagonal=√(l²+b²)
  Triangle: area=½×b×h, perimeter=a+b+c
  Circle: area=πr², circumference=2πr
  Cuboid: volume=l×b×h, TSA=2(lb+bh+lh)
  Cube: volume=a³, TSA=6a²
  Cylinder: volume=πr²h, CSA=2πrh, TSA=2πr(r+h)

PROFIT AND LOSS — SHORTCUT:
  Profit% = (SP-CP)/CP × 100
  If profit% = loss% on different items, net result is always loss
  Net loss% = (x²/100)% where x = common profit/loss %

STATIC GK PRIORITY FOR RRB NTPC:

INDIAN HISTORY:
  Ancient: Harappan script (undeciphered), Ashoka's dhamma, Chandragupta Maurya
  Medieval: Babur (1st battle of Panipat 1526), Akbar's Din-i-Ilahi
  Modern: 1857 - First War of Independence | 1885 - INC founded
    Gandhi's movements: Non-Cooperation (1920), Civil Disobedience (1930), Quit India (1942)

GEOGRAPHY:
  Himalayan ranges: Himadri, Himachal, Shivaliks (inner to outer)
  Indian rivers: Ganga tributaries (Yamuna, Son, Ghaghra, Gandak, Kosi)
  States and capitals: all 28 states + 8 UTs
  Tropic of Cancer: passes through 8 states (Gujarat to Tripura)
  National Parks: Kaziranga (one-horned rhino), Gir (Asiatic lion), Sundarbans (tiger)

SCIENCE:
  SI units: length-metre, mass-kg, time-second, current-ampere, temperature-kelvin
  Speed of light: 3×10⁸ m/s | Sound in air: 343 m/s
  Vitamin A (retinol, night blindness) | B1 (thiamine, beri-beri) | C (scurvy) | D (rickets)
  Blood: groups A/B/AB/O | Rh factor | Universal donor: O negative | Universal recipient: AB+