Question

On a road trip, a driver achieved an average speed of (48.0+A) km/h for the first 86.0 km and an average speed of (43.0-B) km/h for the remaining 54.0 km. What was her average speed (in km/h) for the entire trip? Round your final answer to three significant figures.

Answer 1

Answer:

45.94 km/h

Explanation:

Let the average speed be 48km/h for the first 86 km and 43 km/h for the remaining 54 km. We can calculate the time it takes to travel each of the segment:

For the first 86 km segment:

$t_1 = s_1/v_1 = 86 / 48 = 1.79 hours$

For the remaining 54 km segment:

$t_2 = s_2/v_2 = 54 / 43 = 1.256 hours$

So the total times it takes is

$t = t_1 + t_2 = 1.79 + 1.256 = 3.047 hours$

And the total distance she travels:

$s = s_1 + s_2 = 86 + 54 = 140 km$

The average speed for the entire trip would be total distance divided by total time:

$v = s / t = 140 / 3.047 = 45.94 km/s$