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