Crossing Bridge Interview Puzzle
Four people are on this side of the bridge. the bridge will be destroyed by a bomb in 17 minutes. everyone has to get across before that. Problem is that it’s dark and so you can’t cross the bridge without a flashlight, and they only have one flashlight. Plus the bridge is only big enough for two people to cross at once. The four people walk at different speeds: A fella is so fast it only takes him 1 minute to cross the bridge, B takes 2 minutes, C 5 minutes, the D it takes 10 minutes to cross the bridge. when two people cross the bridge together (sharing the flashlight),
they both walk at the slower person’s pace. can they all get across before the bridge blows up? Mentioning the speeds once again :
Person A: 1 minute
Person B: 2 minutes
Person C: 5 minutes
Person D:10 minutes
Of course its possible, otherwise it wouldn’t be a very interesting question. The only trick is in realizing that you want to get the two slowest people across together, because otherwise you are wasting too much time. Then once you get them across, how do you not make one of them walk back with the flashlight. Well, you just have one of the fast people already there waiting to sprint the flashlight back across.1. A & B cross. total time: 2 minutes.
C ,D |==========================| A,B(flash light)
2. B comes back. total time: 4 minutes.
3. C & D cross. total time: 14 minutes.
B |==========================| A,C,D(FL)
4. A comes back. total time: 15 minutes.
B,A(FL)|==========================| C ,D
5. A & B cross. total time: 17 minutes.
|========= =============| A,B,C,D
More puzzles to try-
- 3 + 3 = 3 5 + 4 = 4 1 + 0 = 3 2 + 3 = 4 ...Read More »
- There are 10 stacks of 10 coins each. Each coin weights 10 gms. However, one stack of coins is defective ...Read More »
- Which clock works best? The one that loses a minute a day or the one that doesn’t work at all?Read More »
- Paul, Sam and Dean are assigned the task of figuring out two numbers. They get the following information: Both numbers ...Read More »
- Five puzzleFry ship’s pirates have obtained 100 gold coins and have to divide up the loot. The pirates are all ...Read More »
- Four days are there which start with the letter ‘T‘. I can remember only two of them as “Tuesday , Thursday”. ...Read More »
- Two fathers took their sons to a fruit stall. Each man and son bought an apple, But when they returned ...Read More »
- A farmer is taking her eggs to the market in a cart, but she hits a pothole, which knocks over ...Read More »
- Let it be simple and as direct as possible. Interviewer : Tell me how much time (in days) and money would ...Read More »
- Solve this logic sequence puzzle by the correct digit- 8080 = 6 1357 = 0 2022 = 1 1999 = ...Read More »
- A man leaves his house in the morning to go to office and kisses his wife. In the evening on ...Read More »
- Jasmine, Thibault, and Noah were having a night out and decided to order a pizza for $10. It turned out ...Read More »
- Which letter replaces the question markRead More »
- A murderer is condemned to death. He has to choose between three rooms. The first is full of raging fires, ...Read More »
- Richie established a very strange number system. According to her claim for different combination of 0 and 2 you will ...Read More »
- The result of math class test came out. Fariha’s mark was an even number. Srabon got a prime!! Nabila got ...Read More »
- Robi is a very serious student. On the first day of this year his seriousness for study was 1 hour. ...Read More »
- Ragib: I got digits of a 2 digit number Sakib: Is it an odd? Ragib: Yes. Moreover, the sum of ...Read More »
- If u r genius solve it:- 40 * 14 = 11 30 * 13 = 12 20 * 12 = ...Read More »
- When do we call “10” while looking at number “2”?Read More »