Rule of 72 / 70 / 114 Estimator mechanism

Model scope

Rule 72 for doubling, Rule 70 as an alternate doubling approximation, and Rule 114 for tripling are standard quick approximations when the rate is entered in percentage points. Verdict is NEEDS_REVIEW because the spec does not explicitly resolve the input representation (for example, 6 versus 0.06) or define the required positive, nonzero rate constraint.

No additional formula finding is recorded.

Units and conventions

• The input must be an annual percentage expressed in percentage points: 6 means 6% per year, not 0.06.
• The formulas assume a constant annual rate and return approximate years.
• The rate is nominally annual; compounding frequency and reinvestment assumptions are not represented.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "rate_percent": 6
  },
  "expected_outputs": {
    "years_to_double_rule72": 12,
    "years_to_triple_rule114": 19,
    "years_to_double_rule70": 11.6666666667
  },
  "working": "Double using Rule 72: 72 ÷ 6 = 12 years. Triple using Rule 114: 114 ÷ 6 = 19 years. Alternate double using Rule 70: 70 ÷ 6 = 11.6666666667 years."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

A zero annual rate makes every formula undefined, so the instrument must reject it. A convention mismatch between percentage points and decimal fractions can also produce results differing by a factor of 100. Negative or nonpositive rates should likewise be validated because the raw arithmetic can produce meaningless negative or undefined times.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json