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Question 2724: Area of a Half-Open Integer-Endpoint Rectangle

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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R0004-02724 · q-20261005-advance-20261006-r06-area-0049

Original question and givens

Use one equal-unit orthonormal Euclidean Cartesian frame. For the half-open rectangle [-27, -23)×[11, 35), find the exact area in squared length units.

  • G001 — Use one equal-unit orthonormal Euclidean Cartesian frame. For the half-open rectangle [-27, -23)×[11, 35), find the exact area in squared length units.

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

orthonormal equal-length coordinate units;half-open regions

After

area in squared length units

Conditions: none

Axes are orthogonal with equal length units;half-open boundaries make adjacent unit cells disjoint.Area uses squared units,not length units.

Step identifiers and dependencies

Rule: half_open_area_convention · Uses: G001

S002 · calculation

Before

coordinate rectangle width := sub(-23, -27)

After

coordinate rectangle width = 4

Conditions: none

Right minus left is the nonnegative width;translation of the origin contributes no area.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

coordinate rectangle height := sub(35, 11)

After

coordinate rectangle height = 24

Conditions: none

Top minus bottom is the nonnegative height,using endpoints of the same rectangle.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

coordinate rectangle area := mul(4, 24)

After

coordinate rectangle area = 96

Conditions: none

Rectangle area is width times height;a zero side makes the half-open rectangle empty,with area0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · implies

Before

[-27, -23, 11, 35]

After

area=96

Conditions: none

Endpoints may coincide but may not be reversed;compute side lengths before multiplying,not products of coordinates.

Step identifiers and dependencies

Rule: rectangle_area_boundary · Uses: G001, S004

Reverse checks

  • S005 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S004 · premise_and_result_audit — Recompute coordinate rectangle area with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute coordinate rectangle height with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute coordinate rectangle width with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

96

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: 66f67aaf38f0a1c578a30717e281ed468c46cf8941138d746db5d0d069ebaad4
  • candidate record SHA-256: 73de2c75b74ef05fc409a71d7eda4b46eed81b7840e1c8518f5038894391250e
  • semantic review receipt SHA-256: 312ae86315346b8955842a547cb2d09246e1f826755f72c2a51f042e5c7d5c56
  • question-first witness SHA-256: 831f449ed41ff9144a290e534aa32adf7252d15b81c16ed5886a7dfd65dee70c
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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