Puzzle n°17 (*) - Crossing the bridge Homepage  

Once upon a time, during a very dark night, a group of 4 cat buddies were travelling together.
They had to cross a river. There was a bridge, but this bridge was not strong enough to stand more than 2 cats at a time,
and extremely dangerous because it was very narrow and had no safety rails on the side.
The night was so dark, that even cats could not get a glimpse of the surroundings,
and they were in dire need of an external light otherwise, they would fall in the ravine below for sure...
Fortunately, they had an electric torch in the group, but only one.
Besides, this torch had a very short battery : 17 minutes autonomy only.

The group included a persian, who would take a good 10 minutes to cross the bridge,
a british shorthair who could cross in 5 minutes,
a somali who would need 2 minutes to cross the bridge,
and a very quick abyssinian who would only need 1 minute !

Persian British Shorthair Somali Abyssinian
10 min. 5 min. 2 min. 1 min.


They were all sitting there in front of the bridge, discussing how to proceed
so that the 4 of them arrive safely on the other side of the ravine.
They took time to build up a strategy, taking care of not lighting up the torch before they needed it,
in order to save its full autonomy for bridge crossings.

They were saying :
"You, the aby, you're the quickest. If you cross with the Persian first,
then bring back the torch, then cross with the British Shorthair, then finally come back for the Somali,
this would take 10 minutes + 1 to come back + 5 minutes + 1 to come back + 2 minutes.
The total is 19 minutes... Hell, the torch would run out just when you were ready to cross with the Somali...
No, we can't do it like this !

Can you help them find a better solution ?

... I'm giving up ...


© Marie-Bernadette Pautet, 2005-2019
Last page update: 10.4.2007