The Old Man And The Street
 

An old man leaves a pub and starts to "walk" home. The man's speed is 3 km/h and his poor little house lies outside the village (the exact distance pub-house is 4.5 km).

When the man starts, his dog runs home and back to him on an on, at a speed twice as the old man's speed. So the distances, the dog is running between the man and his house are decreasing until the distance is zero and they both arrive at the tiny old house of the old man.

Premium question: what distance does the dog run? 8)

9 km .. assuming the man returning from the pub can walk in a straight line ;)

How did you sum up the partial distances of the dog? ;)

[quote="koal"]How did you sum up the partial distances of the dog? ;)[/quote]

You don't need to sum any series, and the 3km speed is irrelevant. The dog is runing twice as fast as the man. So in the time that the man walks the 4.5km to home, the do will travel twice that far or 9km.

:banana:

[quote="Gary Edstrom"]You don't need to sum any series, and the 3km speed is irrelevant. The dog is runing twice as fast as the man. So in the time that the man walks the 4.5km to home, the do will travel twice that far or 9km.[/quote]
What speed is the dog going when he changes directions?

[quote="Xyzzy"]What speed is the dog going when he changes directions?[/quote]
Twice the speed the man is going when [u]he[/u] changes directions. :)

Huh?

Does the man change directions?

[quote="Xyzzy"]Huh?

Does the man change directions?[/quote]
Yeah, when he finds a five dollar bill on the ground and goes back to the pub :shock: ;) :D .

Wouldn't it be a five-pound note? or do they take american currency in the UK?

Because koal is from Austria, I guess it would be a five-euro note. :D