SOLUTION: On a 100km track a train travells the first 30km at a uniform speed of 30km/h . How fast must the train travel the next 70 km so as to average 40km/h for the entire trip?

Question 1084090: On a 100km track a train travells the first 30km at a uniform speed of 30km/h . How fast must the train travel the next 70 km so as to average 40km/h for the entire trip?
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Rate x Time = Distance,
For the first 30 km,

So then to get the average velocity,
Using the distance formula,
1.
and using the average velocity,
2.
So then,

Substituting into 1,

So then from 1,

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