Which formula is used to calculate average velocity?

V Subscript a v g Baseline = StartFraction x Subscript f Baseline minus x Subscript I Baseline over t Subscript f Baseline minus t Subscript i Baseline EndFraction
V Subscript a v g Baseline = StartFraction t Subscript f Baseline minus t sub I over x sub f minus x sub I
v Subscript a v g Baseline = StartFraction d over t EndFraction
v Subscript a v g Baseline = StartFraction t over d EndFraction