Counting a residue class in a thousand-number interval

Proved

WorkbookSource.problem_7425

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

How many integers between $1000$ and $2000$ are congruent to $2 (mod 7)?$

Source: InternLM Lean-Workbook, record lean_workbook_7425 (Apache-2.0). The complete source proposition and its explicit variable declarations are preserved.

Preamble

import Mathlib
open Real Nat

Formal statement

theorem WorkbookSource.problem_7425 : Finset.card (Finset.filter (λ x => x % 7 = 2) (Finset.Icc 1000 2000)) = 143  :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, record lean_workbook_7425; Apache-2.0

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