Mr. X lives in A-City and wants to visit B-city. There are 1000 km between these 2 cities.
So, Mr. X takes his car and drives to go to B-City. At halfway of his ride (500 km), he realises that his average speed has been 100 km/h, from A-City to now.
What is the average speed that he has to drive from now to B-City, in order to have an average speed of 200 km/h on the full ride (from A-City to B-City) ?
Answer
Needed speed for 2nd half:
infinity km/hour
Because:
200 km/hour for 1,000km trip = 5 hours which he has already spent driving!
5 hours driven at 100km per hour = 500km or halfway there. He has already driven 5 hours at the halfway point. To average 200km for the trip he needs to be at city B in 5 hours from the start which allows no more time for the 2nd half of the trip
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