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Question 30886: Combinations Including or Excluding a Fixed Existing Label

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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R0060-30886 · q-20261011-advance-20261015-r06-permutation-combination-0061

Original question and givens

Select distinct labeled objects without replacement. Ordered and unordered selections are different; the empty selection counts exactly once, with no circular or indistinguishable-object model. n=11≥1, k=2, fixed existing label 0. Give (all combinations, combinations containing 0, combinations excluding 0, sum of the two parts minus the whole).

  • G001 — Select distinct labeled objects without replacement. Ordered and unordered selections are different; the empty selection counts exactly once, with no circular or indistinguishable-object model. n=11≥1, k=2, fixed existing label 0. Give (all combinations, combinations containing 0, combinations excluding 0, sum of the two parts minus the whole).

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

source roles = [qf-density15-selection-one-distinguished-counts, density15_selection_one_distinguished_counts, finite_distinct_selection_protocol]

After

derived = [[total, included_label0, excluded_label0, partition_defect]]

Conditions: none

density14/15 use FULL-prefix underscores;density17 uses LOCAL hyphens.The coordinate and circle frames differ.Retain THIS family ordered answer roles/types and all original bilingual JSON/status.

Step identifiers and dependencies

Rule: R60_EXACT_perbank_operation_domain_FRAME_and_output_roles · Uses: G001

S002 · calculation

Before

Selection all subsets ordered ORIGINAL available-choice factor0 := mul(1, 11)

After

Selection all subsets ordered ORIGINAL available-choice factor0 = 11

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

Selection all subsets ordered ORIGINAL available-choice factor1 := mul(11, 10)

After

Selection all subsets ordered ORIGINAL available-choice factor1 = 110

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · implies

Before

source roles = [Selection all subsets ordered, 11, 2]

After

derived = [[11, 10], 110]

Conditions: none

At position j there are n-j UNUSED distinct labeled objects.Multiply ALL k available-choice counts;at k0 there is exactly ONE empty ordered tuple.This is not replacement,circular or indistinguishable selection.

Step identifiers and dependencies

Rule: Selection_ORDERED_distinct_without_replacement_available_choices · Uses: G001, S003

S005 · calculation

Before

Selection all subsets within-subset ORIGINAL factorial factor2 := mul(1, 2)

After

Selection all subsets within-subset ORIGINAL factorial factor2 = 2

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · implies

Before

source roles = [Selection all subsets within-subset, 2]

After

derived = [2]

Conditions: none

Multiply the COMPLETE2..n factors;at n0/1 the empty product is1.Use exact BigInt,not floats or a SAFE cap on derived counts.

Step identifiers and dependencies

Rule: Selection_factorial_COMPLETE_integer_product_EMPTY0factorial1 · Uses: G001, S005

S007 · calculation

Before

Selection all subsets ORIGINAL exact ordered over k factorial := div(110, 2)

After

Selection all subsets ORIGINAL exact ordered over k factorial = 55

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · calculation

Before

Selection all subsets reverse unordered times k factorial := mul(55, 2)

After

Selection all subsets reverse unordered times k factorial = 110

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S007

S009 · implies

Before

source roles = [Selection all subsets, 11, 2, 110, 2]

After

derived = [55, 110]

Conditions: none

EACH k-subset has exactly k! orderings,so P/k! is the exact integer C.Multiply back to verify P.An empty subset and empty ordering each count once;no probability model is asserted.

Step identifiers and dependencies

Rule: Selection_UNORDERED_each_subset_has_kfactorial_orderings · Uses: G001, S008

S010 · calculation

Before

Selection subsets INCLUDING label0 ordered ORIGINAL available-choice factor0 := mul(1, 10)

After

Selection subsets INCLUDING label0 ordered ORIGINAL available-choice factor0 = 10

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S009

S011 · implies

Before

source roles = [Selection subsets INCLUDING label0 ordered, 10, 1]

After

derived = [[10], 10]

Conditions: none

At position j there are n-j UNUSED distinct labeled objects.Multiply ALL k available-choice counts;at k0 there is exactly ONE empty ordered tuple.This is not replacement,circular or indistinguishable selection.

Step identifiers and dependencies

Rule: Selection_ORDERED_distinct_without_replacement_available_choices · Uses: G001, S010

S012 · implies

Before

source roles = [Selection subsets INCLUDING label0 within-subset, 1]

After

derived = [1]

Conditions: none

Multiply the COMPLETE2..n factors;at n0/1 the empty product is1.Use exact BigInt,not floats or a SAFE cap on derived counts.

Step identifiers and dependencies

Rule: Selection_factorial_COMPLETE_integer_product_EMPTY0factorial1 · Uses: G001, S011

S013 · calculation

Before

Selection subsets INCLUDING label0 ORIGINAL exact ordered over k factorial := div(10, 1)

After

Selection subsets INCLUDING label0 ORIGINAL exact ordered over k factorial = 10

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S012

S014 · calculation

Before

Selection subsets INCLUDING label0 reverse unordered times k factorial := mul(10, 1)

After

Selection subsets INCLUDING label0 reverse unordered times k factorial = 10

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S013

S015 · implies

Before

source roles = [Selection subsets INCLUDING label0, 10, 1, 10, 1]

After

derived = [10, 10]

Conditions: none

EACH k-subset has exactly k! orderings,so P/k! is the exact integer C.Multiply back to verify P.An empty subset and empty ordering each count once;no probability model is asserted.

Step identifiers and dependencies

Rule: Selection_UNORDERED_each_subset_has_kfactorial_orderings · Uses: G001, S014

S016 · calculation

Before

Selection subsets EXCLUDING label0 ordered ORIGINAL available-choice factor0 := mul(1, 10)

After

Selection subsets EXCLUDING label0 ordered ORIGINAL available-choice factor0 = 10

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S015

S017 · calculation

Before

Selection subsets EXCLUDING label0 ordered ORIGINAL available-choice factor1 := mul(10, 9)

After

Selection subsets EXCLUDING label0 ordered ORIGINAL available-choice factor1 = 90

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S016

S018 · implies

Before

source roles = [Selection subsets EXCLUDING label0 ordered, 10, 2]

After

derived = [[10, 9], 90]

Conditions: none

At position j there are n-j UNUSED distinct labeled objects.Multiply ALL k available-choice counts;at k0 there is exactly ONE empty ordered tuple.This is not replacement,circular or indistinguishable selection.

Step identifiers and dependencies

Rule: Selection_ORDERED_distinct_without_replacement_available_choices · Uses: G001, S017

S019 · calculation

Before

Selection subsets EXCLUDING label0 within-subset ORIGINAL factorial factor2 := mul(1, 2)

After

Selection subsets EXCLUDING label0 within-subset ORIGINAL factorial factor2 = 2

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S018

S020 · implies

Before

source roles = [Selection subsets EXCLUDING label0 within-subset, 2]

After

derived = [2]

Conditions: none

Multiply the COMPLETE2..n factors;at n0/1 the empty product is1.Use exact BigInt,not floats or a SAFE cap on derived counts.

Step identifiers and dependencies

Rule: Selection_factorial_COMPLETE_integer_product_EMPTY0factorial1 · Uses: G001, S019

S021 · calculation

Before

Selection subsets EXCLUDING label0 ORIGINAL exact ordered over k factorial := div(90, 2)

After

Selection subsets EXCLUDING label0 ORIGINAL exact ordered over k factorial = 45

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S020

S022 · calculation

Before

Selection subsets EXCLUDING label0 reverse unordered times k factorial := mul(45, 2)

After

Selection subsets EXCLUDING label0 reverse unordered times k factorial = 90

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S021

S023 · implies

Before

source roles = [Selection subsets EXCLUDING label0, 10, 2, 90, 2]

After

derived = [45, 90]

Conditions: none

EACH k-subset has exactly k! orderings,so P/k! is the exact integer C.Multiply back to verify P.An empty subset and empty ordering each count once;no probability model is asserted.

Step identifiers and dependencies

Rule: Selection_UNORDERED_each_subset_has_kfactorial_orderings · Uses: G001, S022

S024 · calculation

Before

Selection ORIGINAL included plus excluded := sum(10, 45)

After

Selection ORIGINAL included plus excluded = 55

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S023

S025 · calculation

Before

Selection ORIGINAL partition sum minus whole := sub(55, 55)

After

Selection ORIGINAL partition sum minus whole = 0

Conditions: none

Use ORIGINAL operands for exact integer/rational arithmetic.Only RAW inputs use SAFE or the explicit family bounds;derived values do not inherit those caps or use floating approximations.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S024

S026 · implies

Before

source roles = [11, 2]

After

derived = [55, 10, 45, 0]

Conditions: none

n>=1 ensures the GIVEN existing label0.Containing it leaves k-1 choices from the other n-1 objects;excluding it chooses k from those n-1.The two classes are disjoint and exhaustive.At k0 inclusion count0,and at k=n exclusion count0 are legal.

Step identifiers and dependencies

Rule: Selection_FIXED_EXISTING_label0_disjoint_complete_subset_partition · Uses: G001, S025

Reverse checks

  • S026 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S025 · premise_and_result_audit — Recompute Selection ORIGINAL partition sum minus whole with exact rational arithmetic, not rounded decimals.
  • S024 · premise_and_result_audit — Recompute Selection ORIGINAL included plus excluded with exact rational arithmetic, not rounded decimals.
  • S023 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S022 · premise_and_result_audit — Recompute Selection subsets EXCLUDING label0 reverse unordered times k factorial with exact rational arithmetic, not rounded decimals.
  • S021 · premise_and_result_audit — Recompute Selection subsets EXCLUDING label0 ORIGINAL exact ordered over k factorial with exact rational arithmetic, not rounded decimals.
  • S020 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S019 · premise_and_result_audit — Recompute Selection subsets EXCLUDING label0 within-subset ORIGINAL factorial factor2 with exact rational arithmetic, not rounded decimals.
  • S018 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S017 · premise_and_result_audit — Recompute Selection subsets EXCLUDING label0 ordered ORIGINAL available-choice factor1 with exact rational arithmetic, not rounded decimals.
  • S016 · premise_and_result_audit — Recompute Selection subsets EXCLUDING label0 ordered ORIGINAL available-choice factor0 with exact rational arithmetic, not rounded decimals.
  • S015 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S014 · premise_and_result_audit — Recompute Selection subsets INCLUDING label0 reverse unordered times k factorial with exact rational arithmetic, not rounded decimals.
  • S013 · premise_and_result_audit — Recompute Selection subsets INCLUDING label0 ORIGINAL exact ordered over k factorial with exact rational arithmetic, not rounded decimals.
  • S012 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S011 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S010 · premise_and_result_audit — Recompute Selection subsets INCLUDING label0 ordered ORIGINAL available-choice factor0 with exact rational arithmetic, not rounded decimals.
  • S009 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S008 · premise_and_result_audit — Recompute Selection all subsets reverse unordered times k factorial with exact rational arithmetic, not rounded decimals.
  • S007 · premise_and_result_audit — Recompute Selection all subsets ORIGINAL exact ordered over k factorial with exact rational arithmetic, not rounded decimals.
  • S006 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S005 · premise_and_result_audit — Recompute Selection all subsets within-subset ORIGINAL factorial factor2 with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.
  • S003 · premise_and_result_audit — Recompute Selection all subsets ordered ORIGINAL available-choice factor1 with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute Selection all subsets ordered ORIGINAL available-choice factor0 with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Reverse-check using the ORIGINAL data,types,indices and premises.Consistency auditing does not claim the conclusion uniquely determines its inputs.Keep finite candidates,independent review,formal proof and publication separate.

Result

(55, 10, 45, 0)

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: 3bf93d2ef7c470a08572b02b5249a13cc53c52e87cb9f366db4673e862cd6a1c
  • candidate record SHA-256: 0fe2a14d822bbb6e1c537c1de28b89ef775bfe16da5c69f7878b1a0a94dece6e
  • semantic review receipt SHA-256: d6b5a409bf933281a46617cd715d8016fd5ca3d6fb76f77d179ac2ecd9d608bf
  • question-first witness SHA-256: f80ecf598c6893a580af018e1a82849b33ee6887efb48a6a1d69569aa17f12e4
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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