How to calculate 'Average velocity' in the different scenarios ?

If a body has covered a distance at speed 'v₁' (half of the distance) and then with a speed 'v₂'(the other half of the distance), then

for 'n' equal parts of distances

If an object travels with velocity v₁ for the first half of time, and with velocity v₂ for the second half of time then

If an object travels with velocities v₁, v₂, v₃ etc., during time intervals t₁, t₂, t₃ etc.,

then v_ave =

if t₁ = t₂ = t₃ = ..... t
then v_ave =

If a body has an initial displacement position x₁ at time t₁ undergoes motion attains final displacement x₂ at time t₂, then

If x₁, x₂ .... x_n are the displacement made by the body for time t₁,t₂, . . . . t_n, then