MCN Professionals | Interview Question of the day
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Today's Question:
There is a bridge, which will collapse in 17 minutes. 4 people (A, B, C and D) are
standing on one side of the bridge and want to cross it before it collapses. There are few restrictions, as below:
- It's dark, so you can't cross the bridge without a
torch(flashlight), and there is only one torch.
- The bridge is only big/strong enough for 2 people to cross at a time.
- All 4 people walk at different speeds.
- A takes 1 minute
- B take 2 minutes
- C take 5 minutes, and
- D takes 10 minutes
to cross the bridge.
- When two people cross the bridge together (sharing the torch), they
both walk at the speed of slower person.
How can they all get across before the bridge blows up (i.e cross the bridge in 17 minutes)?
The solution to the above problem is as follows:
| Move | Time |
| A & B Cross with torch | 2 |
| A returned with torch | 1 |
| C & D Cross with torch | 10 |
| B returned with torch | 2 |
| A & B Cross with torch | 2 |
|
|
| Total | 17 |
Hence all, A,B,C and D will cross the Bridge in 17 minutes.
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