You want to figure out distance per second. One way to do this is calculate distance apart at t=0,1,2…
The difference between each point would be the average speed over that second.
Using sqrt(b2+g2):
t0 = 0
t1 = 1.554m
s1 = (1.554m-0m)/1s = 1.554m/s
t2 = 3.108m
s2=(3.108m-1.554m)= 1.554m/s
As you continue this you will see they travel at a constant speed apart from each other. The reason this is working is because you need to divide distance by time. Dividing by 1 second won’t change the value of the number after you subtract. If you notice you can do (t2-t0)/2s and also get the same answer.
Well that’s my point. The answer is correct in this specific case, because it’s already “built-in” so to speak.