# Thread: 3 logic problems for the price of one

1. ## 3 logic problems for the price of one

problem 1
A version of this I saw on the labrinth except this one is a lot more complicated (I think I might have seen it on a website while I was transversing or something can't remember where tho).

What you got:
3 men 1 who tells the truth 1 who lies and one randomly says yes and no.

The problem:
1 of the men is holding a key and you only get to ask the men three questions.

problem 2
This one's an easy one with many solutions that we did in logic class

What you got:
A 3 liter jug a 5 liter jug, an infinate amount of water, and a big tub (infinately large)

The problem:
you need to fill the big tub with 9 liters of water

problem 3
This one is a math problem I pulled from a website I'll cite it when everything is done:

What you got: the numbers 3 3 7 7

The problem: you need to get 24 using only addition, multiplication, division and subtraction. everything is in base 10 and no decimal's where used and you need to use all 4 numbers only once.

2. I love those kind of problems. Post more please or email them to me. Thank you.

3. ## Easy...

The first one: Just ask each one "Who has the key?"

Second one: Fill the 5 litre jug, pour it into the 3, and the overfill goes into the tub
Repeat once.
Fill and pour the 5 litre jug into the tub

The last one might take more than 5 seconds...

Must we use all 4 digits?

Because 3*7+3 = 24

4. Problem 1:
the guy who tells the truth and the guy who lies will always answer predictably so when you find the only one where they say yes/no to, the one random guy will simply say yes/no and if he changes his answer then you know he's the random guy...

Problem 2:
I think you messed up the final size, because getting 9 liters with a 3 liter jug is not hard.. just fill it up 3 times... But if you wanted to do it the hard way, just use the overflow from the 5 to the 3 in order to get 2 liters and then do the math from there.

Problem 3:
hmmm not entirely sure
(3 * 7) + 3 but then there's a 7 left over....

5. your missing the line where it says you need to use "all 4 numbers once." And you need to get a key I thought that needing to get the key was implyed

6. Problem 1:

<still working on it>

Problem 2:

Option 1: Fill the three liter jug three times, emptying it each time into the tub.

Option 2: Fill the 5 liter jug and pour it into the 3 liter job, allowing the remaining two liters to overflow into the tub. Do this again, so that you have a total of 4 liters in the tub. Finally, fill the 5 liter container and poor the whole thing into the tub.

Problem 3:

7*(3+3/7) = 24

7. way to go avdven
I messed up on the second one it's supposed to be 3, 7 and 8 but I'm tired and messed up oh well.

8. Zepherin: I am unable to find a solution for the first problem. I had it figured out (I figured out who had the key), but in order to actually get the key, it would require a 4th question (or at least a command telling the person with the key to give it to you). I can also figure out who is who (which is the truth teller, which is the liar, and which is the one who answer ambiguously), but, once again, once I have information, getting the key would require another question. Any hints?

AJ

9. 77 - 3 / 6 =24.66666666666666666

but we're not using decimals so 77 - 3 / 6 =24

advens answer looks much more correct (and i thought i tried that!?!)

3 gal jug 3 times

can't get the key yet!

10. ## Revised solution 2

Originally posted here by zepherin
I messed up on the second one it's supposed to be 3, 7 and 8 but I'm tired and messed up oh well. [/B]
Solution:

Fill 7 liter jug and pour into 3 liter jug, allowing the remaining 4 liters to flow into the tub. Repeat to add another 4 liters, and you have a total of 8 liters.

AJ

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