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# Bridge brainteaser

## Bridge brainteaser

(OP)
Four people arrive at a river with a narrow bridge that can hold a maximum of two people at a time.
It's nighttime and they have only one flashlight that MUST be used when crossing the bridge.
Person A can cross the bridge in one minute
Person B in two minutes
Person C in five minutes
Person D in eight minutes.

What's the fastest way they can all get to the other side of the bridge?

### RE: Bridge brainteaser

Swim across the river.

### RE: Bridge brainteaser

(OP)
Note: that if two people go across the bridge at the same time they move at the slower person's pace.

### RE: Bridge brainteaser

#### Spoiler:

A carries the flashlight the entire time; A crosses with B, goes back and crosses with C, goes back and crosses with D. Having the quickest person be the one to make the return trip with the flashlight minimizes the total time since each person must cross at least once.
That assumes the flashlight can't be thrown back to the others who are waiting.

Andrew H.
www.mototribology.com

### RE: Bridge brainteaser

(OP)
MotoLuber -

The total time for your solution is 17 minutes.
A and B Cross = 2 min
A returns = 1 min
A and C cross = 5 min
A returns = 1 min
A and D cross = 8 min

There is another faster way.

#### Spoiler:

If C and D cross together, you are saving some time.... as follows:
A and B Cross = 2 min
A returns = 1 min
C and D cross = 8 min
B returns = 2 min
A and B cross = 2 min
Total Time = 15 min

### RE: Bridge brainteaser

Ah...those darn maths always get me. I'll see myself out

Andrew H.
www.mototribology.com

### RE: Bridge brainteaser

#### Spoiler:

en.wikipedia.org/wiki/Bridge_and_torch_problem

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