Answer:
200 km
Explanation:
Let's use the formula:
distance = rate × time
Let the original average speed of the car be r km/h, and let the distance between the two cities be d km.
According to the problem, the car takes 2 hours to cover the distance, so we have:
d = r × 2
If the car's average speed decreased by 20 km/h, its new average speed would be (r - 20) km/h. If it took 30 minutes (0.5 hours) longer to cover the same distance at the slower speed, we have:
d = (r - 20) × 2.5
Now we have two equations for d:
d = r × 2
d = (r - 20) × 2.5
We can solve for r in the first equation:
r = d / 2
Substituting into the second equation:
d = (d/2 - 20) × 2.5
Simplifying:
d = 1.25d - 50
0.25d = 50
d = 200
Therefore, the distance between the two cities is 200 km.
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