Firstly SI units must be used so 1 mile = 1069,344 metres. Thus 1.5 miles = 2414,016 m
Now SI unit for time is seconds so 0.5 hours = 1800 seconds
Now speed is equal to distance over time thus 2414,016 ÷ 1800 = 1,34
The unit for this is metres per second = m.s^-1
Now speed is a scalar quantity which has no direction but has magnitude thus the speed is 1,34 m.s^-1
And velocity is a vector quantity thus it has both magnitude and direction thus the velocity us 1,34 m.s^-1, south
Note that speed is equal to velocity the only difference is that one must have direction and one must not have direction, due to the scalar and vector property l.
