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Logic and IQ Challenge

Let's test each other's logic and IQ with mind-bending questions. We post questions, and whoever has an answer can just PM it to whoever posted the question. You can also ask for clues or nudges to make things easier.

I'll start the ball rolling with some moderate questions. Some of you may already have heard or seen some of these, but please keep the answers to yourselves.

Once you thought of the answer, you'll just know it's the precise answer - so if you have any apprehensions and are quite unsure about your solution, then maybe it is the answer. Remember, all the questions and solutios below are logical.

1. it was an unusually dark night, which means that visibility is poor. Unfortunately for four people, they are being chased by a vile creature. They have quite a head start, and they are gaining pace against the monster. However, they came across a very old and rather long wooden hanging bridge (with missing steps), where only two people at the same time can cross. Problem is, they only have one flashlight they can use to guide them as they traverse the bridge. This means that only two persons can cross first, one carrying the flashlight, and after they both reach the other end, one should go back and perhaps fetch another person.

But here's the deal: person A can cross the bridge in 10 minutes, person B in 5 minutes, person C in 2 minutes, and person D in 1 minute. Whenever 2 persons are crossing simultaneously, whichever is the logner time counts. And supposing the creature can't reach them for a good 17 minutes, what is the logical order (of crossing the bridge) the people should follow that would only take up 17 minutes?

2. There is a big and an unusually enclosed house that has no windows and has only one door. Outside, there are three switches and inside, there is a single light bulb. Your problem then is to find which among the three switches opens the light inside. The light is not visible from the outside and the door is at the opposite side of the switches. So checking inside the door while tinkering with the switches is impossbile. Even though you can switch the switches as much as you like, once you open the door, you have to enter and you won't be able to come out again. Now, what should you do to determine which switch opens the light given that you'll be locked in once you enter?

Hint: You can use objects around you, although limit yourselves with what's given.

That's it for now.

Comments

  • bananalubebananalube NOSEBLEED PExer
    Let me just correct one of my sentence above. Instead of "Once you thought of the answer, you'll just know it's the precise answer - so if you have any apprehensions and are quite unsure about your solution, then maybe it is the answer", it should be, "Once you thought of the answer, you'll just know it's the precise answer - so if you have any apprehensions and are quite unsure about your solution, then maybe it is not the answer".
  • munchy_munchmunchy_munch Member PExer
    ANS: #1

    1. Let C and D cross the bridge first.
    2. Let C goes back to the other side of the bridge to bring the
    flashlight.
    3. Then Let A and B cross the bridge together.
    4. Then Let D goes back to the other side of the bridge to
    fetch C.
    5. Last pair to cross the bridge C and D.

    Sol'n
    A = 10 C = 2
    B = 5 D = 1
    TIME CONSUME
    1. C & D = 2
    2 C = 2
    3. A & B = 10
    4. D = 1
    5. C & D = 2
    17 mins

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