A marble rolls 5.2 m in 1.8 s. Roughly what is its average speed?

1. Average speed = distance travelled / time taken = 5.2 m / 1.8 s. 2. As a quick sanity check: 5 m divided by 2 s is about 2.5 m/s, which is close to the exact value. 3. The text's discussion confirms this estimate: "Since 2.5 m/s is close to 2.9 m/s, the answer is reasonable." 4. 1.8 m/s repeats the given time value and 5.2 m/s repeats the given distance value -- neither is the computed ratio. 5. So the marble's average speed is about 2.9 m/s, roughly a brisk walking pace. _Source: OpenStax Physics Ch 2 "Motion in One Dimension", p.65 Worked Example §2.2 Speed and Velocity_