Quiz - Mind Trap

Jalli · Post by **Jalli** » 15 Dec 2003, 17:28

btw, Phillip got the 1000! one

A = n = 1

chux · Post by **chux** » 15 Dec 2003, 18:33

meh, I was right in saying theres a ! at the end...!
And I was just about to say it was 1 too, bah

Phillip · Post by **Phillip** » 15 Dec 2003, 19:06

jw wrote: if A have to be a whole number you would like to find a real lot of following numbers that are not primes, so you would need the biggest prime number...
hmm, if you know the biggest prime number you may tell me and mail me the proof for it

Yes, A has to be a whole number.

You do not need the "biggest" prime number. Actually it has been prooven that there are infinitely many prime numbers, so there is no biggest prime number.

You CAN actually express A as a function of n which gives A+1, ..., A+n not primes. Can you do it?

To clarify:
I want to find 10000 following numbers that are not primes. I plug the number into the formula for A(n=10000), and get the answer. A+1, A+2, ..., A+10000, of which none are primes.

And yes, it is possible to find as many following numbers not primes as you want, even though there are infinitely many prime numbers. (Strange, huh?)

And no, Jalli, A is not 1, because already the first number after 1 (2) is a prime

Jalli · Post by **Jalli** » 15 Dec 2003, 20:27

I had a feeling something was wrong yes

How bout this one: A = n = 0

Jalli · Post by **Jalli** » 15 Dec 2003, 23:06

1: It is easy to "build up" 21 using +-*/ and the numbers 2, 3, 5, 6 like this:

(2+5)*(6-3)

Your task now is to build up 21 using 1, 5, 6 and 7...

2: You want 4 liters with water. You have one cup that takes 5 liters and one that takes 3. You have unlimited watersupply. How will you get those 4 liters that you want?

3: You've got two hourglasses. One 4 minute and one 7 minute. How are you supposed to measure up 9 mins.

4: On a table you have got to ironsticks, one red and one blue. Besides the color only one thing separates them. One of them is a magnet. Everything else is the same. Next to those on the table there are these things:

A glass filled with water, a 5 1/4"discett, a ball of twine.

How can you, by the use of the things mentioned above, find out which of the two which is the magnet?

jw · Post by jw » 16 Dec 2003, 05:44

Jalli wrote: 2: You want 4 liters with water. You have one cup that takes 5 liters and one that takes 3. You have unlimited watersupply. How will you get those 4 liters that you want?

you put in one cup 5 liter, you take out 3 liter you have 2 left in the 5 liter cup than. you throw the 3 liter away and put the 2 liter in the 3 liter cup. then you take 5 liter in the 5 liter cup and pour 1 liter in the 3 liter cup (there is allready 2 so you know when to stop) than you have 4 liter left in the 5 liter cup

jw · Post by jw » 16 Dec 2003, 05:51

Jalli wrote:3: You've got two hourglasses. One 4 minute and one 7 minute. How are you supposed to measure up 9 mins.?

you start with the 4 and 7 min hourglasses at the same time, when the 4 min is past, you turn it upside down. when the 7 min glass is finished the 9 minutes start, and there is 1 minute left in the 4 min. hourglass, when this one is finished you put it upside down, and when it is finished you put it upsidedown again and when it is finished again 9 min have passed since the 7 min. hourglass is finished.

jw · Post by jw » 16 Dec 2003, 05:57

Jalli wrote: 4: On a table you have got to ironsticks, one red and one blue. Besides the color only one thing separates them. One of them is a magnet. Everything else is the same. Next to those on the table there are these things:

A glass filled with water, a 5 1/4"discett, a ball of twine.

How can you, by the use of the things mentioned above, find out which of the two which is the magnet?

hmm, probably i don't understand the question, but to find out which of the two ironsticks is a magnet you can put the iron parts of the floppydiscett near the ironsticks. (what is twine, and i'm not sure about the 5 1/4"discett, what is it? does it fit in the glass? you mean you should build a compass from those parts? )

jw · Post by jw » 16 Dec 2003, 06:42

Jalli wrote:1: It is easy to "build up" 21 using +-*/ and the numbers 2, 3, 5, 6 like this:

(2+5)*(6-3)

Your task now is to build up 21 using 1, 5, 6 and 7...

7 â€“ 6 â€“ 1 x 5 = 0
( 5 + 7 ) / 6 - 1 = 1
( 5 + 7 ) / 6 x 1 = 2
5 + 6 - 7 -1 = 3
6 - 7 + 5 x 1 = 4
5 + 7 - 6 - 1 = 5
7 - 6 + 5^1 = 6
7 - 6 + 5 + 1 = 7
6 - 5 + 7 x 1 = 8
6 - 5 + 7 + 1 = 9
5 x (7 â€“ 6 + 1) = 10
(7 - 5) x 6 - 1 = 11
5! / 6 - 7 - 1 = 12
(7 - 5) x 6 + 1 = 13
5! / 6 - 7 + 1 = 14
√(5 - 1) + 7 + 6 = 15
? = 16
5 - 1 + 6 + 7 = 17
5 x 1 + 6 + 7 = 18
5 + 1 + 6 + 7 = 19
√(5 - 1) x 7 + 6 = 20
7 x 6 / √(5 â€“ 1) = 21

But how to build up 16?

jw · Post by jw » 16 Dec 2003, 12:38

Phillip wrote: To clarify:
I want to find 10000 following numbers that are not primes. I plug the number into the formula for A(n=10000), and get the answer. A+1, A+2, ..., A+10000, of which none are primes.

A could be: (2^20996011)-1
(this was Jalli's answer, but this one work with A+1, A+2, ..., A+10000)

Phillip · Post by **Phillip** » 16 Dec 2003, 15:25

jw wrote: A could be: (2^20996011)-1
(this was Jalli's answer, but this one work with A+1, A+2, ..., A+10000)

None of you seem to have understood the question. You are supposed to find a formula for A, like:

A(n) = 3n + 5n^2

(this example is completely wrong, of course)

The formula should guarantee that the next n numbers after A(n) are not primes. It is a simple formula... (hint: it involves !)

zworqy · Post by **zworqy** » 17 Dec 2003, 10:33

jw wrote:
Jalli wrote: 4: On a table you have got to ironsticks, one red and one blue. Besides the color only one thing separates them. One of them is a magnet. Everything else is the same. Next to those on the table there are these things:

A glass filled with water, a 5 1/4"discett, a ball of twine.

How can you, by the use of the things mentioned above, find out which of the two which is the magnet?
hmm, probably i don't understand the question, but to find out which of the two ironsticks is a magnet you can put the iron parts of the floppydiscett near the ironsticks. (what is twine, and i'm not sure about the 5 1/4"discett, what is it? does it fit in the glass? you mean you should build a compass from those parts? )

twine = thin rope
I don't quite remember whether 5 1/4" floppy's has some metal parts, but that sounds too easy anyway...

zworqy · Post by **zworqy** » 17 Dec 2003, 12:44

Here's one for you:

Wilbur was out bicycling, when his friend gave him a little push in his right side. Which way (left or right) should Wilbur turn to avoid falling off his bicycle, and why??

Jalli · Post by **Jalli** » 17 Dec 2003, 13:55

He should lean towards left in order to get his bicycle "straight" again.

And btw jw, no square roots in order to make 21, just parantheses and +-*/

2 and 3 you solved

chux · Post by **chux** » 17 Dec 2003, 19:20

He should go with the push...or put his foot down

Juski · Post by **Juski** » 12 Feb 2004, 03:18

Revolt wrote:2. Sid Shady, who was sporting a large fresh bump on his forehead, was found lying on the pavement just below the jewellerâ€™s window. The ambulance attendants were reviving the unconscious Shady when detective Shadow arrived on the scene. Shadow questioned several eye witnesses and arrested Shady the moment he was coherent. Shady did not have a criminal records nor had he confronted or spoken to anyone that day. Why would shadow arrest him?

You miss spelled 'coherent' it supposed to be 'proven guilty'.[/quote]

chux · Post by **chux** » 12 Feb 2004, 16:18

Nah, 'coherent' makes sense, it means 'makes sense', so when he was back to normal after being knocked out, he was arrested...

Juski · Post by **Juski** » 11 Mar 2004, 14:14

Pretty long that it has been no posts in this great topic so time to 'live it up' with one(!) of my own riddles i just made up:

What is it that you can take but not steal.

(you can take meal but you can steal it from someone else too)

Crazy · Post by **Crazy** » 11 Mar 2004, 14:50

I guess answear could be my own life..

(Maybe that's a bad swedish translation of riddle)

EtanOli · Post by **EtanOli** » 11 Mar 2004, 14:52

a breath

Juski · Post by **Juski** » 11 Mar 2004, 18:46

Both were rigth but i thought of life, and it's a perfectly fine translation of an swedish riddle.

Jalli · Post by **Jalli** » 3 May 2004, 22:32

Just found this fun riddle in another forum; please solve yourself instead of googling:

A child is 21 years younger than the mother. Six years from now, the mother will be five times older than the child.
Question: Where's the father?

EtanOli · Post by **EtanOli** » 3 May 2004, 23:05

ages in years:
x=child now
y=mother now

present time:
x=y-21

+6 years:
5(x+6)=y+6

->
y=5x+24
x=5x+24-21
4x=-3
x=-0,75 ;-9 months, daddy's in da house

teajay · Post by **teajay** » 4 May 2004, 01:27

heh, I also came up with that, but I thought it was meant to be a joke; like father wasn't there, bleh.

I guess i'm too simple...

Jalli · Post by **Jalli** » 4 May 2004, 14:55

EtanOli wrote:ages in years:
x=child now
y=mother now

present time:
x=y-21

+6 years:
5(x+6)=y+6

->
y=5x+24
x=5x+24-21
4x=-3
x=-0,75 ;-9 months, daddy's in da house

Perfectly correct =)

jonsi · Post by **jonsi** » 4 May 2004, 20:59

our teacher would never accepted that.
she would want x on both sides.
i think that x on both sides would be more logic and correct than that with x and y

Jalli · Post by **Jalli** » 4 May 2004, 21:34

heh, oki, you do teh maths:

x=x-21

after 6 years:
5(x+6)=x+6

If you find possible x here please let me know

jonsi · Post by **jonsi** » 5 May 2004, 08:00

i would like this

kid x
mum x+21

sixyears later

5(x+6)=x+21+6
5x+30=x+27
4x=-3
x=-0.75

jonsi · Post by **jonsi** » 5 May 2004, 08:02

a new problem

itis a triangle
the base is 2 km long
the lft angle is 82degrees and the right one is 78degrees
the upper is 20degrees
how tall is the triangle

Post by **SveinR** » 5 May 2004, 15:38

Well I must use a calculator here, but fuck it:

c = 2km
A = 82 degrees
B = 78 degrees
C = 20 degrees

Then I whane find teh side 'b':

b/sin B = c/sin C

b = (c*sin B)/sin C = (2*sin 78)/sin 20 = 5,7

Then the area (hmm i feel this method is too slow and there probably is a faster one):

T = 1/2 *b*c* sin A = 1/2 * 5,7 * 2 * sin 82 = 5,65

Height, then, is: (let's call it 'm')

T = (c*m)/2

m= 2T/c = 2*5,65/2 = 5,65

So the height is 5,65km

Vaitork · Post by **Vaitork** » 5 May 2004, 18:04

SveinR wrote:b = (c*sin B)/sin C = (2*sin 78)/sin 20 = 5,7

5,7198 to be more precise...

Just multiply side b with sin A to get the height (faster method)

5,7198 * Sin 82 = 5,6641 Km.

chux · Post by **chux** » 5 May 2004, 18:10

OMG you would get it before I had a chance to show off...

teajay · Post by **teajay** » 5 May 2004, 18:52

heh, always funny when you see

through a maths assignment!

Post by **SveinR** » 6 May 2004, 17:09

Vaitork wrote: 5,7198 to be more precise...

5,7198 * Sin 82 = 5,6641 Km.

What's the point in being this precise?

Vaitork wrote:Just multiply side b with sin A to get the height (faster method)

Ahh, of course..

Ky.Jelly · Post by **Ky.Jelly** » 9 Feb 2005, 12:16

bout itme this got going again, feeling in teh mood for some smarts

jw · Post by jw » 9 Feb 2005, 14:15

ky, you know one for me?

teajay · Post by **teajay** » 9 Feb 2005, 20:30

Proove me that this formula ^^ is correct.

Rez · Post by **Rez** » 9 Feb 2005, 20:32

q: whats x? i cant see

teajay · Post by **teajay** » 9 Feb 2005, 20:41

The length of AD

jw · Post by jw » 9 Feb 2005, 22:09

hmm, you mean this:

XÂ² = (BC)Â² + 2Â²
XÂ² = (BC)Â² + 4
XÂ² - 4 = (BC)Â²
√ (XÂ² - 4) = √ [(BC)Â²]
√ (XÂ² - 4) = BC

teajay · Post by **teajay** » 9 Feb 2005, 22:14

Thanks. I didn't say it wasn't simple, but I had trouble with it.

(I didn't solve it myself)

BTW, step 4 is pretty unneccesary.

jw · Post by jw » 9 Feb 2005, 22:35

for me step 2, 3 and 4 are all very useless, i just saw it, my thirst thougt was: does he want us to proof pythagoras was right?

A1 = cÂ²
A2 = ab/2
Atotal = (a + b)Â²
Atotal = A1 + 4(A2) = cÂ² + 4(ab/2)

so:

(a + b) Â² = cÂ² + 4(ab/2)
aÂ² + bÂ² + 2ab = cÂ² + 2ab
cÂ² = aÂ² + bÂ²
aÂ² + bÂ² = cÂ²

Ky.Jelly · Post by **Ky.Jelly** » 10 Feb 2005, 07:47

jw wrote:ky, you know one for me?

nope, not right now, but from the looks of what youve done most would be to easy