2 min lesson
The 60-Minute Run, Step by Step
Walk through "The 60-Minute Run, Step by Step" in order, then name the proof that tells you it worked.
Step 1 of 2
Interactive diagram. Step through it with the Next and Previous controls below, or Tab to a region to read its detail.
diagram: flow
Three tasks plus the sanity gates that turn correct-by-luck into correct-by-rigor.