Rule of 72 / 70 / 114 Estimator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t4-116

Effect

Computation or source lookup only

Input and validation requirements

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.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "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."
}

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