Average speed = total distance / time
1) Distance from A to B
Distance = velocity * time = V1 * t1 = 5.10 t1
2) Distance from B to A
Distance = velocity * time = V2*t 2 = 2.75 t2
Distance from A to B = distance from B to A => 5.10t1 = 2.75t2
=> t2 = 5.10t1 / 2.75
3) Average speed = total distance / total time =
total distance = 2 * 5.10 t1 = 10.20 t1
Average speed = [10.20 t1] / [t1 + 5.10 t1 / 2.75]
As you see t1 is factor for the three terms, so you can simplify it
=> Average speed = [10.20 ] / [1 + 5.10/2.75] = 3.57 m/s
Answer: 3.57 m/s
