Double: Years = 72 / Rate
Triple: Years = 114 / Rate
Quadruple: Years = 144 / Rate
Reverse: Rate = 72 / Years (or 114, 144)
Trick: 72 has many factors (2,3,4,6,8,9,12) making division easy. For 114, think 114 = 6 x 19.
Simple: SI = P x r x t
Compound: Final = P x (1 + r)^t
Trick: For 2 years compound: multiply by (1+r) twice. Split into parts — e.g. 1000 x 1.08 = 1000 + 80 = 1080, then 1080 x 1.08 = 1080 + 86.4
Gross margin: (Revenue - COGS) / Revenue
Net margin: Net Income / Revenue
ROE: Net Income / Equity
ROA: Net Income / Assets
Trick: Think fractions — 30/200 = 15/100 = 15%. Cancel zeros first.
Current ratio: Current Assets / Current Liabilities
Quick ratio: (Cash + Receivables) / Current Liabilities
D/E ratio: Debt / Equity
Trick: Simplify both numbers by dividing by common factors. 150/100 = 1.5
Earnings yield: = 1/PE = 100/PE (as %)
PEG ratio: = P/E / Growth rate
Rule of 20: Fair P/E = 20 - Inflation
Stock price: = EPS x P/E
Trick: PE of 20 → yield = 5%. PE of 10 → yield = 10%. They're inverses.
Fair price: P = Dividend / (r - g)
Implied return: r = (Div / Price) + g
Trick: Focus on the spread (r - g). If r=10%, g=5%, spread = 5% = 0.05. Then divide: $5 / 0.05 = $100. Move decimal 2 places.
Simple perpetuity: V = CF / r
Growing perpetuity: V = CF / (r - g)
Terminal value: TV = FCF / (WACC - g)
Trick: Same formula! Convert % to decimal, then divide. $10M / 5% = $10M / 0.05 = $200M. Multiply by 20 is the same as dividing by 0.05.
PV: CF / (1 + r)^t
CAGR (doubled): ≈ 72 / years
CAGR (tripled): ≈ 114 / years
Trick: For PV, know common powers: 1.1² = 1.21, 1.1³ = 1.331. At 10% discount, $1000 in 2yr ≈ $826.
Current yield: Coupon / Price x 100
Annual coupon: Par x Coupon rate
Duration impact: Price Δ ≈ -Duration x Yield Δ
Trick: Duration 5, yield up 1% → price down ~5%. Yield down → price up. It's a simple multiply.
BE units: Fixed Costs / (Price - Variable Cost)
BE revenue: Fixed Costs / CM%
CM%: (Price - VC) / Price x 100
Trick: Find contribution margin per unit first (Price - VC), then divide fixed costs by it.
Question: What % equity do you need to call?
Formula: Equity = Call / (Pot + Call + Bet)
Example: Pot $100, villain bets $50.
Call = $50. New pot = $100 + $50 + $50 = $200
Equity needed = $50 / $200 = 25%
Question: How often must villain fold for your bluff to profit?
Formula: Break-even = Bet / (Pot + Bet)
Example: Pot $100, you bet $75.
Break-even = $75 / ($100 + $75) = $75 / $175 = 42.9%
Question: How many combos of a hand remain?
Pairs: C(available suits, 2) = n(n-1)/2
4 suits available = 6 combos, 3 = 3, 2 = 1
Suited: Count suits available in both ranks
Offsuit: Cross product of available suits, minus suited combos
Tip: Remove suits blocked by hero hand and board cards
Question: Estimate your equity with a draw
Rule of 4 (flop, 2 cards to come):
Equity = Outs x 4 - max(0, Outs - 8)
Rule of 2 (turn, 1 card to come):
Equity = Outs x 2.2
Common draws: Flush draw = 9 outs, OESD = 8, Gutshot = 4, Overcards = 6
Question: Select all hands in a given range
Grid layout: Pairs on diagonal, suited above, offsuit below
Scoring: IoU (Intersection over Union) - need 70%+ match
Tip: Start with premium pairs, then add broadways, then suited connectors