lean_workbook_plus_34502

Proved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

Consider the ends of the ruler as marks too. With $n$ marks, we can measure $\binom{n}{2}$ lengths, since we can (only) measure distances between any pair of marks. So we need $\binom{n}{2} \ge 16$ , giving $n \ge 7$ . In other words, we need 5 extra marks besides the endpoints.

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_34502  (n : ℕ)
  (h₀ : 0 < n)
  (h₁ : n.choose 2 ≥ 16) :
  5 ≤ n - 2   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook

View graph