Julie drives 100 mi to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at 33.0 and half the distance at 80.0 . On her return trip, she drives half the time at 33.0 and half the time at 80.0 . What is Julie's average speed on the way to Grandmother's house? What is her average speed on the return trip?
Average speed is ALWAYS calculated as total distance / total time total distance is 100mi total time is (50mi / 33) + (50mi / 80) total time is = 1.52 + 0.625 = 2.145 so average speed going to grandmothers house is 100mi / 2.145 hrs = 46.62 mph
on her return trip x = V1 x t/2 + V2x t/2 100 = 33t/2 + 80t/2 100 = 113t/2 t = 100x2/113 = 1.7699hrs average speed = 100mi/1.7699hrs = 56.60mph
