lean_workbook_plus_14323

Disproved

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

Kate rode her bycicle for $40$ minutes at a speed of $16$ mph, then walked for $90$ minutes at a speed of $4$ mph. What was her overall average speed in miles per hour?\n\n $\text{(A)}\ 7 \qquad \text{(B)}\ 9 \qquad \text{(C)}\ 10 \qquad \text{(D)}\ 12 \qquad \text{(E)}\ 14$ \n\nyeah, i remember this from the 10 i think \n\n $\frac{1}{2}16+\frac{3}{2}4=14$ \n\n $\frac{14}{2}=\boxed{7}$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_14323  (kate_biking_time kate_biking_speed kate_walking_time kate_walking_speed : ℝ)
  (h₀ : 0 < kate_biking_time ∧ 0 < kate_biking_speed ∧ 0 < kate_walking_time ∧ 0 < kate_walking_speed)
  (h₁ : kate_biking_time = 40 / 60)
  (h₂ : kate_biking_speed = 16)
  (h₃ : kate_walking_time = 90 / 60)
  (h₄ : kate_walking_speed = 4) :
  (16 * ((40 / 60 + 90 / 60) / 2) + 4 * ((40 / 60 + 90 / 60) / 2)) / (40 / 60 + 90 / 60) = 7 / 2   :=  by sorry

Source

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

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