The speed of the yacht : 100 km/h
Linear motion consists of 2: constant velocity motion with constant velocity and uniformly accelerated motion with constant acceleration
the speed of vo = v = constant
acceleration = a = 0
Δx = vt or x = xo + vt
An equation of constant velocity motion
[tex]\large {\boxed {\bold {x = v \times \: t}}}[/tex]
x = distance = m
v = speed = m / s
t = time = seconds
A yacht sailed at a steady speed for 0.5 hours, and traveled 50 kilometers
so the velocity/speed:
[tex]\tt v=\dfrac{x}{t}\\\\v=\dfrac{50~km}{0.5~h}=\boxed{\bold{100~km/h}}[/tex]