The applet can help you to understand speed as a rate : It is the distance travelled per unit of time.
In the applet, unit for time is seconds, and unit for distance is metres

1. How far (in metres) can the red car go if it continues for 150 seconds
2. How much time (in seconds) will it take the blue car to move 1200 m?
Can you write down the relationship (formula or equation) between distance (d), speed(s) and time (t) using algebraic notation ie d, s and t ?
s = ? (in terms of d & t)
d = ? (in terms of s & t)
t =? (in terms of s & d)