The car covered 400 km. It is known that in the first half of the entire time of movement, he moved at a speed of 90 km

The car covered 400 km. It is known that in the first half of the entire time of movement, he moved at a speed of 90 km / h and in the second half of the time he traveled 175 km. What was the speed of the car on the second leg? Determine the average speed of the vehicle along the way. Consider the movement of the vehicle in both sections uniform.

Given: S = 400 km V1 = 90 km / h s2 = 175 km T1 = T2 = T
Find: Vср -?
Solution: s1 = S – s2 = V1 * T => T = (S – s2) / V1 = (400-175) / 90 = 2.5 (h) V2 = s2 / T = 70 (km / h) Vav = (V1 + V2) / 2 = (90 + 70) / 2 = 80 (km / h)
Answer: 80 km / h.