Quiz, exercising your dog

[Crackle]

Try this one.

Mrs Smith left the house at a walking speed of two kilometers per hour. One hour later, Mr Smith and his dog left the house. Mr Smith wanted to catch up to Mrs Smith and therefore set a pace of four kilometers per hour. His dog was rather excited and ran back and forth between Mr & Mrs Smith, traveling at a speed of ten kph. When Mr Smith finally caught up to Mrs Smith, how far had the dog run?


Mike

[JohnBS]

10km. 1 hour for Mr to catch Mrs.

[Crackle]

Its simpler than it first seems.

[peter scott]

I agree with John. The maximum distance between husband and wife is 2 km. From the time Mr Smith sets off to him meeting her the distance decreases at 2 km/hr. It takes 1 hr for him to catch her and the sum is linear so the average distance between them is 1 km in which the dog runs 10 km always assuming that Mrs Smith is walking in a straight line.

Peter

[westcliff]

I too agree with John. The dog is running for one hour at 10 km/hour.

Gus.

[Crackle]

Yes correct.
Basically if the dog is running at 10 KPH it dose not matter which direction he is running, he will still cover 10K.
The business of running back and forth and diminishing distance is a bit of a red herring.
Mike