This video lesson is an introduction to the formula for distance, constant speed, and time: d = vt (or d = rt if you use r as rate instead of v as velocity).
First I explain an easy way to memorize this formula in the form v = d/t, comparing it to the common way to express the speed of cars, such as 55 miles per hour. Then we solve a few simple problems involving distance, time, and speed using the formula.
Equations with fractions — video lesson
Math Mammoth Grade 7 curriculum (pre-algebra)