Simple constant velocity question

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To average 60 km/h over a 90 km trip, the total travel time must be 1.5 hours. After averaging 40 km/h for the first 40 km, which takes 1 hour, 50 km remains to be covered in 0.5 hours. To achieve this, an average speed of 100 km/h is required for the remaining distance. The calculations confirm that this is the correct approach and answer.
cherryrocket
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7. Q: "If you must average 60 km/h for a 90 km trip, and you only average 40 km/h for the first 40 km, what velocity must you average the rest of the way?"

A:

90 km 60km/h 1.5h
d v t

1st
40 km 40 km/s 1h
d v t

2nd
50 km ? 0.5h (1.5-1h = 0.5h)
d v t

v = d/t = 50km/0.5h = 100 km/h

Is this the right answer and is it the right way of solving it?
 
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Yes, looks right to me.
 

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