In the middle of a dark night, a team of 4 somewhat injured commandoes are on their way back from a tough mission. To complete their return, they have to cross a narrow, dangerous and collapsing bridge. The leader of the team makes some quick estimates:
The bridge would collapse completely in 17 minutes
Due to the injuries, each member would take a different time to cross the bridge. The time for the different members to cross the bridge are 10 min, 5 min, 2 min and 1 min respectively.
Due to the dangers involved, at most two members can travel across the bridge at a time
Moreover, they have only one working flashlight, which means that the flashlight must be carried back for the next pair to cross the bridge
Can they all make it across in time? If so, then how?
2006-09-15 23:16:32 · 11 answers · asked by aashu 1 in Science & Mathematics ➔ Engineering
2 minute and 1 minute cross together with the flashlight: 2 minutes
1 minute crosses back alone with the flashlight: 1 minute
10 minute and 5 minute cross together with the flashlight: 10 minutes
2 minute crosses back alone with the flashlight: 2 minutes
2 minute and 1 minute cross together with the flashlight: 2 minutes
total 17 minutes
2006-09-15 23:36:32 · answer #1 · answered by picopico 5 · 0⤊ 0⤋
1&2 go across first then 2 gos back to the other side and we now have 4 minutes. 2 gives the flashlight to 10&5 and they go across to 1 now we have a total of 14 minutes. 1 takes the light and gos back to get 2 there is now 15 minutes on the clock. 1&2 hurry back across and they both get off the bridge in 17 minutes just at the time of its collaps
2006-09-16 14:28:13 · answer #2 · answered by WOODSMAN 2 · 0⤊ 0⤋
They can't because the leader estimated wrongly and so when the first man sets foot on the bridge the whole thing will collapse in a huge fireball that fries the men that were waiting to cross too.
2006-09-16 06:19:02 · answer #3 · answered by Anonymous · 1⤊ 0⤋
A+B go 2min
A back 1min
C+D go 10min
A follow 1min
so total 14min
I saved 3 min for you in case the leader had estimated wrong.
Explanation : A did not need torch light because he had crossed to and from. He could memorised the bridge holes. :D
2006-09-16 10:32:10 · answer #4 · answered by AAA 2 · 0⤊ 0⤋
Why you want 17 minutes? Within 5 minutes everybody can reach the other side. Just see.
D will carry A in first trip-1 min
D returns -1 min
D carries C in 2nd trip- 1min
D returns- 1 min
D carries B 3rd trip- 1min
total --5 minutes ok
2006-09-16 11:36:27 · answer #5 · answered by kochani 2 · 0⤊ 0⤋
I'm assuming that it's Canadians that are crossing that bridge and they are in Afganistan. So with this in mind they won't make it because the flashlight they use will alert some Air force pilot as to their position and he in turn mows them down in what is called friendly fire.
2006-09-16 06:21:14 · answer #6 · answered by ? 2 · 0⤊ 0⤋
no say one who takes i min-A
2 MIN-B
5 MIN-C AND
10 MIN D
now A and B go it takes - 2min
then A returns- 1min
now a with c goes - 5 min
a returns - 1min
a with d - 10min
a does not return - 0 min
adding
2+1+5+1+10=19
2006-09-16 06:32:42 · answer #7 · answered by hello 2 · 0⤊ 1⤋
No I am too discombobulated to lead an army.
2006-09-17 18:56:54 · answer #8 · answered by Anonymous · 0⤊ 0⤋
Took me some time but it can be done. Nice one.
2006-09-16 06:24:31 · answer #9 · answered by Puppy Zwolle 7 · 0⤊ 0⤋
all will traven in 10min
2006-09-16 09:18:38 · answer #10 · answered by Ravitej 2 · 0⤊ 0⤋