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Bridge Crossing
Thanks Ranish

Five persons are standing on one side of a bridge.
They want to cross the bridge.

Without a torch, they cannot proceed.
Only one torch is available.
The torch has a remaining battery life of only 30 seconds.

Only two people can go over the bridge at one time.
The torch needs to be returned to the remaining persons.

The five people take different times to cross the bridge.
One takes 1 second to cross the bridge.
The others take 3 seconds, 6 seconds, 8 seconds and 12 seconds.

Everyone crosses the bridge within 30 seconds.

Question : How do they proceed?

See answer

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