PERCENTAGE — QUICK METHODS:
  x% of y = y% of x (use this to simplify)
  Successive % change: a% then b% = a + b + ab/100
  Population formula: P(1 + r/100)^n

PROFIT AND LOSS:
  SP = CP × (100 + profit%)/100
  CP = SP × 100/(100 + profit%)
  Discount on MP: SP = MP × (100 - discount%)/100
  Successive discounts d1%, d2%: effective = d1+d2 - d1×d2/100

TIME AND WORK:
  A does in x days → A's 1-day work = 1/x
  A+B together: 1/x + 1/y = 1/(combined days)
  Pipes and cisterns: same concept as time-work

TIME, SPEED, DISTANCE:
  Distance = Speed × Time
  Relative speed (same direction): |S1 - S2|
  Relative speed (opposite): S1 + S2
  Average speed: 2S1×S2/(S1+S2) (harmonic mean)

SIMPLE vs COMPOUND INTEREST:
  SI = P×R×T/100
  CI = P(1+R/100)^T - P
  CI - SI (2 years) = P(R/100)^2

TRIGONOMETRY:
  sin²θ + cos²θ = 1 | 1 + tan²θ = sec²θ | 1 + cot²θ = cosec²θ
  sin 30=0.5 | sin 45=1/√2 | sin 60=√3/2 | sin 90=1
  cos 30=√3/2 | cos 45=1/√2 | cos 60=0.5 | cos 90=0
  tan 30=1/√3 | tan 45=1 | tan 60=√3

GEOMETRY:
  Triangle: area = ½ × b × h | Pythagoras: a²+b²=c²
  Circle: area = πr² | circumference = 2πr
  Sector area = (θ/360) × πr²
  Cylinder: volume = πr²h | CSA = 2πrh | TSA = 2πr(r+h)
  Cone: volume = ⅓πr²h | CSA = πrl | l = √(r²+h²)

CODING-DECODING TYPES:
  Letter coding: A=1, Z=26 or reverse (A=26, Z=1)
  Number coding: each letter gets a number by rule
  Symbol coding: letters replaced by symbols
  Conditional coding: apply conditions to code

  NEW PATTERN (SSC trend): paragraph + code table → decode sentence

BLOOD RELATIONS:
  Draw family tree diagram for complex questions
  Generation level: grandfather(2), parent(1), same(0), child(-1)
  Key: establish anchor person, then map relationships

SERIES PATTERNS:
  Arithmetic: difference constant | Geometric: ratio constant
  Mixed: alternate terms different series
  Prime numbers: 2,3,5,7,11,13,17,19,23...
  Squares: 1,4,9,16,25,36,49,64,81,100
  Cubes: 1,8,27,64,125,216,343

ANALOGY TYPES:
  Synonymy: hot:warm :: cold:cool
  Antonymy: day:night :: white:black
  Functional: doctor:hospital :: teacher:school
  Degree: warm:hot :: cool:cold
  Part-whole: wheel:car :: page:book