Prove2Me

Binomial coefficient identity #59225

Proved
WorkbookCorrected.plus_59225

by carlok · Sep 22, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

((93)∗(63)∗(33))=1680(\binom{9}{3} * \binom{6}{3} * \binom{3}{3}) = 1680

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_59225, which omitted a compilable colon/type annotation and/or used a preamble of only Mathlib.Analysis.Complex.Basic.

Source: InternLM Lean-Workbook, record lean_workbook_plus_59225 (Apache-2.0).

Preamble
import Mathlib.Data.Nat.Choose.Basic
import Mathlib.Tactic.NormNum
Formal statement
theorem WorkbookCorrected.plus_59225 : ((Nat.choose 9 3) * (Nat.choose 6 3) * (Nat.choose 3 3)) = 1680 := by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_59225; Apache-2.0; corrects Open node 6ddcd42e-60b5-429b-b26a-2daa067c1d79

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