# Puzzles/Logic puzzles/Bridge Crossing/Solution

Puzzles | Logic puzzles | Bridge Crossing | Solution

Let's name the four people:

- A - the person who can cross the bridge in 1 minute
- B - the person who can get across in 2 minutes
- C - the person who needs 5 minutes to cross the bridge
- D - the slowest and needs 10 minutes to get across

Now, to make it to the other side in 17 minutes, they do the following

- A & B cross first (total time: 2 minutes)
- A leaves B on the other side and returns with the flashlight (time: 1 minute; total time: 3 minutes)
- C & D cross with the flashlight(time: 10 minutes; total time: 13 minutes)
- B returns with the flash light (time: 2 minutes; total time: 15 minutes)
- Finally, A & B cross to the other side of the bridge (time: 2 minutes; total time: 17 minutes)

Here's a funny poem written by Karen Lingel:

FOUR HUNGRY MEN CROSS A BRIDGE by Karen Lingel, Physicist and Penguinist

*Four men start out to cross the sea*

*And yet they all walk different speeds!*

*The first, a sprinter, he goes fast*

*He leaves the others in the past!*

*The second takes a bit more time*

*[Note to myself: think up a rhyme]*

*The third's a somewhat pokey man*

*He strolls along, sees what he can.*

*The last one is so very slow*

*You'd think he had no place to go!*

*So now they come upon a bridge*

*And on the other side -- a fridge!*

*Well -- you know men -- they've gotta see*

*What's inside the fridge to eat!*

*One flashlight is the light they've got*

*To guide them to the eating spot.*

*The batteries will only last*

*Seventeen minutes -- that's a fact.*

*The bridge, alas, -- and here's the trap --*

*Is apparently a piece of crap.*

*So only two men at a time*

*can cross the bridge -- or they'll sink in brine!*

*How can they all then make the trip?*

*And use the light so no one slips?*

*Send the fast guys first across*

*The fastest returns with little loss.*

*The pokey ones are next to go*

*While Fast Guy waits (they sure are slow)*

*Then send the other fast guy back*

*To get his friend and complete the pack.*

*And this rounds out, for all to see*

*Another FAQ in poetry.*