{
  "schema": "vedokrok.public-item.v1",
  "release_id": "MHC-RPUB-20260920-75ad787a",
  "url": "/knowledge/let-the-units-check-the-formula",
  "id": "MHC-D-RESEARCH-0252",
  "version": "0.1.0",
  "title": "Let the units check the formula",
  "summary": "Units are a second line of reasoning, not decoration after the answer.",
  "kind": "protocol",
  "body": "Keep units attached while calculating. Cancel them algebraically and check whether the remaining unit matches the requested result. A formula that leaves hours squared when you need hours has exposed a problem before the final number can look persuasive.",
  "limits": [
    "Correct dimensions cannot detect every missing factor or incorrect assumption. Squared and cubed units require squared and cubed conversion factors."
  ],
  "topics": [
    "union-numerical-reasoning"
  ],
  "intents": [],
  "source_ids": [
    "RS-8A26862B6CF7036F"
  ],
  "evidence": [
    {
      "claim": "A numerical quantity requires its unit, and valid unit conversions preserve the represented physical quantity.",
      "source_id": "RS-8A26862B6CF7036F",
      "role": "supports",
      "note": "Matching dimensions is a necessary check, not proof that the entire physical model is correct.",
      "locator": "Quantity values and unit notation"
    }
  ],
  "use_when": [
    "A calculation mixes quantities, conversions or rates."
  ],
  "avoid_when": [
    "Correct dimensions cannot detect every missing factor or incorrect assumption. Squared and cubed units require squared and cubed conversion factors."
  ],
  "example": "Dividing 240 records by 60 records per minute leaves 4 minutes; multiplying those inputs does not produce a duration.",
  "check": "Both the number and the resulting unit answer the stated question.",
  "steps": [
    "Write the input quantities with their actual units.",
    "Apply explicit conversion factors and cancel matching units.",
    "Check the output dimension and then check whether the model makes sense."
  ],
  "sources": [
    {
      "id": "RS-8A26862B6CF7036F",
      "title": "SI Unit Rules and Style Conventions Checklist",
      "url": "https://physics.nist.gov/cuu/Units/checklist.html"
    }
  ],
  "relations": [
    {
      "from": "MHC-D-RESEARCH-0252",
      "to": "MHC-D-RESEARCH-0251",
      "type": "useful_with",
      "url": "/knowledge/build-an-overall-rate-from-totals"
    }
  ],
  "collections": [
    {
      "id": "RC-D976097B2A42D9AC",
      "title": "Make the numbers answer the right question",
      "url": "/collections/make-the-numbers-answer-the-right-question"
    }
  ]
}