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Question 6942: Fraction Product and Two Reciprocal Guards

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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R0012-06942 · q-20261011-advance-20261015-r01-fraction-0067

Original question and givens

Use legal integer fraction representations with nonzero original denominators; negative denominators are allowed. Representation and value remain distinct. a=4/3, b=2/-3. Give (product, nonzero eligibility list for a and b separately, their reciprocals or undefined, reciprocal product or undefined).

  • G001 — Use legal integer fraction representations with nonzero original denominators; negative denominators are allowed. Representation and value remain distinct. a=4/3, b=2/-3. Give (product, nonzero eligibility list for a and b separately, their reciprocals or undefined, reciprocal product or undefined).

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

original integer numerator/denominator representations;original denominators nonzero

After

representation and rational value are distinct data

Conditions: none

Negative denominators are valid,but reduced values do not replace original representations.Candidate algorithms about raw numerators/denominators must use those raw data.This finite audit is not a general proof of quotient well-definedness.

Step identifiers and dependencies

Rule: fraction_representation_value_scope · Uses: G001

S002 · calculation

Before

fraction product := mul(4/3, -2/3)

After

fraction product = -8/9

Conditions: none

Multiply the values of the two valid fractions;zero values may still be multiplied.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

fraction reciprocal0 := div(1, 4/3)

After

fraction reciprocal0 = 3/4

Conditions: none

A multiplicative reciprocal exists only when the fraction's value is nonzero.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

reciprocal reverse product0 := mul(4/3, 3/4)

After

reciprocal reverse product0 = 1

Conditions: none

Multiply the value by its reciprocal to check that the result is1.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · implies

Before

value=4/3;nonzero=Yes

After

reciprocal=3/4

Conditions: none

Test whether the value is0,not the sign of the original denominator.A zero numerator over a negative nonzero denominator is valid zero,but has no reciprocal.

Step identifiers and dependencies

Rule: fraction_reciprocal_value_guard · Uses: G001, S004

S006 · calculation

Before

fraction reciprocal1 := div(1, -2/3)

After

fraction reciprocal1 = -3/2

Conditions: none

A multiplicative reciprocal exists only when the fraction's value is nonzero.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · calculation

Before

reciprocal reverse product1 := mul(-2/3, -3/2)

After

reciprocal reverse product1 = 1

Conditions: none

Multiply the value by its reciprocal to check that the result is1.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · implies

Before

value=-2/3;nonzero=Yes

After

reciprocal=-3/2

Conditions: none

Test whether the value is0,not the sign of the original denominator.A zero numerator over a negative nonzero denominator is valid zero,but has no reciprocal.

Step identifiers and dependencies

Rule: fraction_reciprocal_value_guard · Uses: G001, S007

S009 · calculation

Before

product of two reciprocals := mul(3/4, -3/2)

After

product of two reciprocals = -9/8

Conditions: none

Multiply the reciprocals only when both are defined.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S008

Reverse checks

  • S009 · premise_and_result_audit — Recompute product of two reciprocals with exact rational arithmetic, not rounded decimals.
  • S008 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S007 · premise_and_result_audit — Recompute reciprocal reverse product1 with exact rational arithmetic, not rounded decimals.
  • S006 · premise_and_result_audit — Recompute fraction reciprocal1 with exact rational arithmetic, not rounded decimals.
  • 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 reciprocal reverse product0 with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute fraction reciprocal0 with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute fraction product 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

(-8/9, [Yes, Yes], [3/4, -3/2], -9/8)

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: 6fd3ac9ef6e92ae67b0f182c8277a09b46d95f7dada4416c61b207d05952cd69
  • candidate record SHA-256: 3fed3f741106265f02ce3cdb7a1d1b3054fc1e986404ef3b2aa179e9eb60b595
  • semantic review receipt SHA-256: 90dbc494b2d34ef51f412dcff63cfcc1a2215d038bff71f38f5dded4c64faf00
  • question-first witness SHA-256: b72a3b8bcf10f584396e0dd5198c657b0934a71864e5a3fa6321d7a613aef9f9
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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