A boy, a girl and a dog go for a 10 mile walk. The boy and girl can walk at 2 mph and the dog can trot at 4 mph.
They also have a bicycle which only one of them (including the dog!) can use at a time.
When riding, the boy and girl can travel at 12 mph while the dog can pedal at 16 mph.
What is the shortest time in which all three can complete the trip?
(In reply to
re(3): solution by SilverKnight)
Right on. And I agree about replicating the thought process.
What I really want to know is where I can find a dog that rides a bike! I'd like to get a tandem and let the dog do the work. Is that possible? Let's say I weigh 180 pounds, the dog weighs 80 pounds, and the tandem bike weighs 40 pounds. If the dog can pedal the bike at 16 mph by itself, it should be able to pedal at 6.4 mph if I ride along (if the gear ratios are perfect). Show my work? OK!:
Total weight without me = 40 + 80 = 120
Total weight with me: = 120 + 180 = 300
Ratio = 300 / 120 = 2.5
Speed divided by ratio = 16 / 2.5 = 6.4
Now to find the dog....
re(4): solution
