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First part of the ride is 1.5*10 = 15 kilometers.
Second part of the ride is 0.5*13 = 6.5 kilometers.
The entire distance is 15 + 6.5 = 21.5 kilometers.
The total time is 1.5 + 0.5 = 2 hours.
The average rate (or speed) is = kilometers per hour.
This answer is correct, if the path is rectilinear.
Then the speed and the velocity are almost synonymous.
But if the path is curvilinear, then the given data IS NOT ENOUGH to answer the question.
You should know the difference between the rate (= the speed) and velocity.
The first one is a number, while the second one is a vector.