SOLUTION: A man drives 80km/h to Selfoss and 60km/h from Selfoss. What is the average speed? The answer is not 70km/h
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Question 1092797: A man drives 80km/h to Selfoss and 60km/h from Selfoss. What is the average speed? The answer is not 70km/h Found 2 solutions by Boreal, ikleyn:Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! distance= speed* time
Suppose Selfoss is 80 km away
it takes 1 hour to get there and 4/3 of an hour to return.
That would be 7/3 of an hour to drive 160 km
that is 160*3/7 km/h or 68.57 km/h.
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Suppose Selfoss is 60 km away.
It takes 3/4 hour to get there and 1 hour to get back or 7/4 hour to go 120 km
that is 120*4/7 or again 68.57 km/h average speed.
From the other side (or in contrast), it can be solved and has a unique answer under the assumption that
the distance "to there" is equal to the distance back, but it is not stated explicitly in the condition.
