Along a Branch, Multiply
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
When one thing must happen and then another, the chance of both is found by multiplying along the path.
Show
Bike reaches the harbor on time 0.9; the ferry is running 0.8: the whole plan works 0.9 × 0.8 — 0.72.
Watch for
The multiplication is a two-stage count compressed — 90 on-time trips of 100, and eight-tenths of those find the boat.