{
  "address": "1bc2ebfbb4011e1bda2719952d78a8bf",
  "category": "other",
  "question": "How many m2 are in 1 acre?",
  "answer": "4,046.86 m2",
  "askedBy": {
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    "display": "method deck",
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    "id": null
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  "answeredBy": "method",
  "madeAt": "2026-09-30T22:39:30.722Z",
  "validUntil": null,
  "validityClass": "forever",
  "sources": [
    {
      "label": "Guide for the Use of the International System of Units (SI)",
      "url": null
    }
  ],
  "supersedes": null,
  "supersededBy": null,
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  "answerMethod": "method",
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  "source": {
    "kind": "standard",
    "value": "NIST Special Publication 811 (2008 edition), Appendix B.8, Table for length and area (ft2 = 0.3048 m squared; mi2 = 1609.344 m squared; acre = 4046.8564224 m2 exactly; hectare = 10,000 m2 exactly)",
    "retrieved_utc": "2026-09-30T19:29:48Z"
  },
  "qsha256": "cd3892126c3b3101b3227114542efc66720b6ce9695790153ae3afe8b1b0d570",
  "runOne": null,
  "cardContractVersion": "card_contract/1",
  "deck_id": "method-deck",
  "deck_title": "Method Deck",
  "method": {
    "name": "Area conversion",
    "version": "1",
    "source_url_or_file": "methods/area-conversion.cjs",
    "sha256_of_method_file": "fa21cd066f914ad24931310a213d40f9f25a01cc06ed8eca381f96f175f73002"
  },
  "receipt": {
    "inSubstrate": false,
    "local": true,
    "modelCallsAtMint": 0,
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  },
  "method_deck": {
    "inputs": [
      {
        "name": "value",
        "type": "number",
        "unit": "from_unit",
        "required": true,
        "description": "The area to convert"
      },
      {
        "name": "from_unit",
        "type": "string",
        "required": true,
        "description": "Unit of the input value",
        "enum": [
          "m2",
          "ha",
          "km2",
          "ft2",
          "acre",
          "mi2"
        ]
      },
      {
        "name": "to_unit",
        "type": "string",
        "required": true,
        "description": "Unit to convert into",
        "enum": [
          "m2",
          "ha",
          "km2",
          "ft2",
          "acre",
          "mi2"
        ]
      }
    ],
    "outputs": [
      {
        "name": "result",
        "unit": "to_unit",
        "description": "The converted area"
      }
    ],
    "steps": [
      "Look up the exact square-meter equivalent of from_unit and of to_unit.",
      "Convert the input to square meters: sqm = value * m2_per(from_unit).",
      "Convert square meters to the target unit: result = sqm / m2_per(to_unit).",
      "Round result to 6 significant figures."
    ],
    "constants": [
      {
        "name": "m2",
        "value": 1,
        "unit": "m2",
        "source": 0
      },
      {
        "name": "ha",
        "value": 10000,
        "unit": "m2",
        "source": 0
      },
      {
        "name": "km2",
        "value": 1000000,
        "unit": "m2",
        "source": 0
      },
      {
        "name": "ft2",
        "value": 0.09290304,
        "unit": "m2",
        "source": 0
      },
      {
        "name": "acre",
        "value": 4046.8564224,
        "unit": "m2",
        "source": 0
      },
      {
        "name": "mi2",
        "value": 2589988.110336,
        "unit": "m2",
        "source": 0
      }
    ],
    "examples": [
      {
        "name": "worked example",
        "inputs": {
          "value": 1,
          "from_unit": "acre",
          "to_unit": "m2"
        },
        "expected": {
          "answer": "4,046.86 m2"
        },
        "check": "By definition 1 acre = 4046.8564224 m2 exactly; rounded to 6 significant figures is 4046.86."
      },
      {
        "name": "test vector: square kilometers to hectares",
        "inputs": {
          "value": 1,
          "from_unit": "km2",
          "to_unit": "ha"
        },
        "expected": {
          "answer": "100.000 ha"
        },
        "check": "By hand: 1,000,000 m2 / 10,000 m2 = 100 exactly."
      },
      {
        "name": "test vector: square miles to acres",
        "inputs": {
          "value": 1,
          "from_unit": "mi2",
          "to_unit": "acre"
        },
        "expected": {
          "answer": "640.000 acre"
        },
        "check": "By hand: 2,589,988.110336 m2 / 4046.8564224 m2 = 640 exactly, matching the known fact that 1 square mile = 640 acres."
      }
    ],
    "disclaimer": null,
    "deck_category": "units"
  },
  "status": "minted",
  "kind": "method",
  "provenanceClass": "own_question",
  "provenance": {
    "schema": "card_provenance/2.0.0",
    "chain": [
      {
        "source": {
          "kind": "standard",
          "value": "NIST Special Publication 811 (2008 edition), Appendix B.8, Table for length and area (ft2 = 0.3048 m squared; mi2 = 1609.344 m squared; acre = 4046.8564224 m2 exactly; hectare = 10,000 m2 exactly)",
          "retrieved_utc": "2026-09-30T19:29:48Z"
        },
        "sha256": "08d54cd0072f73f3adde275d09deda6050a10ae81c9d0554fb1528e704f60cca",
        "supersedes": null,
        "added_utc": "2026-09-30T22:39:30.722Z",
        "added_by": "method:Area conversion",
        "why": "the method that computed this answer",
        "check": null,
        "status_label": "pending",
        "signature": null
      }
    ]
  }
}