The skater ran the first half of the track at an average speed of 6 m / s

The skater ran the first half of the track at an average speed of 6 m / s, and the second at an average speed of 12 m / s. determine the average driving speed.

Average travel speed:
Vav. = S / t, where S is the total distance traveled (S = S1 + S2, where S1 = 1/2 S, S2 = 1/2 S), t is the total travel time (t = t1 + t2).
S1 = V1 * t1, S2 = V2 * t2, V1 = 6 m / s, V2 = 12 m / s.
Movement time when passing S1, S2:
t1 = S1 / V1 = (1 / 2S) / 6; t2 = S2 / V2 = (1 / 2S) / 12.
Let’s calculate the average speed:
Vav. = S / t = S / ((1 / 2S) / 6 + (1 / 2S) / 12) = S / (0.0833S + 0.0417S) = 1 / 0.125 = 8 m / s.
Answer: The average speed of movement is 8 m / s.