Speed Times Time

Distance equals speed times time. Drive at 60 miles per hour for 2.5 hours and you cover 150 miles. Walk at 3 mph for 45 minutes (0.75 hours) and you cover 2.25 miles. The same formula works at any scale.

Rearranging gives two more equations: speed equals distance divided by time, and time equals distance divided by speed. These three forms answer every "how far," "how fast," and "how long" question. Navigation apps run the same algebra millions of times per second, updating your arrival time as your speed changes.