# 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.*