Warning: Don't read other posters' comments unless you give up since it usually contains the answer. A spy plane with four soldiers inside crash in the enemy's territory. Fortunately, all of them survives. However, two of them got badly wounded. Another one is lightly wounded, and the other one is totally fine. They know they'll be captured soon since they are in the enemy's territory. Luckily, it's night and it's very dark, so they have a chance to avoid the enemy by getting out from their territory really quickly. When they attempt to get out of the territory, they encounter a very long and deep river, and there is only one very narrow bridge. Because of the crappy condition of the bridge, it can only afford two people at the same time. They can't swim on the river, and they fall from the bridge, they'll certainly die. Now these four soldiers have only one flashlight and they need to cross the bridge quickly since the enemy is close behind. The first soldier (A) is the fittest one and he is not wounded, so he can cross the bridge in 5 minutes. The second solider (B) is only slightly wounded and he can cross the bridge in 10 minutes. The third soldier (C) is badly wounded and he can cross the bridge in 20 minutes. And the last one (D) is the most badly wounded and he can cross the bridge in 25 minutes. Because it's very dark and there's only one flashlight, two soldiers have to cross the bridge together at one time. Therefore the time required to cross the bridge is always equal to the longer time between the two soldiers. For example, if A (5 minutes) and C (20 minutes) cross together, it requires 20 minutes to cross the bridge since A has to accompany C crossing the bridge with one flashlight. Then one (or two?) soldier has to come back with the flashlight so that the other two can cross the bridge. Unfortunately, the flashlight only has 60 minutes left in its battery. And the enemy is close behind, but if the soldiers can all make it to the other end of the bridge in 60 minutes and cut the bridge, they all will be save. How would they do it?
A&B cross - 10 minutes A comes back - 5 minutes C&D cross - 25 minutes B comes back - 10 minutes A& B cross - 10 minutes Total Time: 60 minutes Again, though, this took them a few minutes to figure out, making it take about 62 minutes, meaning that A&B are dead before the could finish crossing.
First the 10 minute and 5 minute crosses. - 10 minutes Then the 5 minute dude returns. - 15 minutes Then the 25 and 20 minute dudes go across. - 40 minutes. The 10 minute dude goes back. - 50 minutes The 5 and 10 minute dudes go back across and everyone is safe. - 60 minutes. Of course by the time they think of this they are all captured so it's kinda moot but what are you gonna do?
damnit major, you even made the same observation about them getting screwed due to thinking of the solution. i hate you... oh and this is dylan again hehe
Major got it. I'll be on 1 week vacation without Internet access (shoot!!). I'll post more logic riddles when I come back on Monday March 3rd. Until then.
