The first third of the track was driven by the car at 120 km / h, the second third at 45 km / h

| January 10, 2021 | education

The first third of the track was driven by the car at 120 km / h, the second third at 45 km / h, and the last – at 40 km / h. Find the average speed of the car along the way.

1. Vehicle speed on the first third of the track: V1 = 120 km / h;
2. Vehicle speed on the second third of the track: V2 = 45 km / h;
3. Vehicle speed on the last third of the track: V3 = 40 km / h;
4. Length of the route: S km;
5. Travel time for each third of the route:
T1 = (S / 3) / V1 = (S / 3) / 120 = S / 360 hours;
T2 = (S / 3) / V2 = (S / 3) / 45 = S / 135 hours;
T3 = (S / 3) / V3 = (S / 3) / 40 = S / 120 hours;
6. Total travel time of the route: T hour;
T = T1 + T2 + T3 = S / 360 + S / 135 + S / 120 = S / 54 hours;
7. Travel speed of the highway: Vcp km / h;
Vcp = S / T = S / (S / 54) = 54 km / h.
Answer: the average speed of the car along the way is 54 km / h.



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