(PLEASE GIVE BRIANLIEST)
The average speed is not equal to the sum of the speeds divided by 2 because the car takes different times to cover the distance while going up and coming down the hill.
The average speed can be calculated as the total distance covered divided by the total time taken. As the speeds are constant, we can use the formula:
distance = speed * time
Let the distance traveled be "d". The time taken to go up the hill is "t1" and the time taken to come down is "t2".
d = 35 * t1 = 69 * t2
The total time taken for the round trip is t1 + t2.
The average speed is given by:
average speed = d / (t1 + t2) = d / (d/35 + d/69)
So the average speed can be calculated as follows:
average speed = d / (d/35 + d/69) = d * (35 + 69) / (35 * 69) = 104 / 2445 = 8 / 205 km/h