/sci/ - Science & Math

I shoot you and steal all your money. Fake or not there's still a shitload of real gold there.

i don't think you thought this through when designing the problem...the sacks are supposed to weigh the same otherwise the fake one weighs less than the real one

>>1451750
whoops re-read the problem, the fake one would weigh *more* than the real one

>>1451744
Why not just take one coin from sack each and put them on the scale?
OP is a faggot

transmute all gold into lead, find the one golden-looking coin

You take one from the first sack, two from the second etc, and check how much they weight at total.
Then you check the difference with the result you get and the you result you would get if they were all real gold. 1g difference? First sack. 2g? Second. And you get the point, hopefully.

tl;dr:Faggot.

Arbitrarily label the sacks A and B.
Put a coin from sack A on the scale. TARE the scale.
Put the coin from A back in A. Put a coin from B on the scale.
Read the scale. If it says -1g, the B coins are fake. If it says +1g, the B coins are real.

Why the fuck is the fake one more massive?
Platinum, iridium, rhenium, neptunium and plutonium, the only metals denser than gold, are all worth more than gold.

I'm taking the fakes.

I lol'd when i realized everyone above this post red the third word of the op, ten, as a two.

I would weigh the biggest bag, if it is not an even number thats the fake.

>>1451766

This man winz!

>>1451793

lol i fucked up too. i mean if it ends in an even number, its the fake.

>>1451790
>plutonium
>metal

>>1451790
business major detected

>>1451744
>n sacks of equal amount of gold coins
Amount referring to value or weight?

>>1451895

Quantity

>>1451802
>implying plutonium isn't a metal

they usually just leave it in whatever ion form and don't bother reducing it, but it is a metal.

*Throw both bags down from a building, compare in-air time.
*Take on coin from one of the bags, if it weights 9g then it is true gold.
*You put both on the scale and take one off and calculate the weight of each bag.
*Use the equal number trick

why is everyone reading it as 2 sacks? it says ten (10)

I take the two sacks, and when I get home, I'll see which one is good.

>>1452330

lrn2binary faggot

>>1451744

This is so simple /sci/.

9 sacks weigh 10x (where x is the number of coins in each bag)

the other sack only weighs 9x.

>>1452345

>You have a scale.You can only use it once (read what it says only ONCE).

HURR DURR HURP DURPPP DURRR

shit nigga i didmt know u could take the fucking coins out

fuck you op

Divide the contents into little piles of 1, 2, 3, etc until you reach 10, while making sure to remember which sac they're from. Then put them on the scale. Then you can solve this with basic math (trial and error, seeing what fits if the fake pile had 4 coins, 5 coins, etc)

I know i didnt write that out well, but you get it.

>>1451741

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wow, epic facepalm at almost everyone in this thread...

>equal amount of coins in each sack
>not equal mass of coins in each sack
>Given the weight properties listed in the op,
>I don't even need the fucking scale, I just leave the heavier sack sitting on the ground and take the lighter one

Okay, so the sack with the gold coins will weigh less than the sack with the fake coins in it?

Put both sacks on the scale and see which one weighs more. Duh.

You must use prime numbers, you need 1 coin from first bag, 2 coins from second one, 3 coins from third, 5 coins from fourth etc

you put both sacks on the scale

>>1452374

put on 9 sacks if it weights 100 its the other sack thats got the fake.
if not take off one sac at a time till the difference is 9 g rather than 10.

>>1452398
also i did this problem the way it should be written.
real sac = 10g
fake = 9

>>1452398

but you can only read the scale once.

I'll just take 9 random sacks and bolt.
How's that, OP?

I think everyone is pretending they think it says two sacks because they are afraid of their own insecurities at not being able to solve the problem.

>>1451766
>You have a scale.You can only use it once (read what it says only ONCE).
>(read what it says only ONCE).

>>1452378
>We have ten sacks

>>1451744
>implying you need a scale for 1 gram of difference.

Pick up each one, the heaviest it the fake gold.

>>1452425
>He thinks he can feel a difference of 1 gram

Curiously enough, this question appeared as a bonus item in one of my geology exams. I spent most of the time on this problem since I finished early on the actual exam.

Too bad I still couldn't get the correct solution to this problem.

I'm sure fake gold makes different sounds, take a coin from each and hit it against each other.

>>1452445
Firstly it's an unspecified amount of coins, plural, so it's at minimum 2 grams difference. Secondly, Yes.

take 2 coins from 1st bag
take 3 coins from 2nd bag
take 5 coins from 3rd bag
take 7 coins from 4th bag
take 11 coins from 5th bag
take 13 coins from 6th bag
take 17 coins from 7th bag
take 19 coins from 8th bag
take 23 coins from 9th bag
take 29 coins from 10th bag

put all coins on scale, determine their weight minus 10449 grams
if the result is:
2 grams ... 1st bag is fake
3 grams ... 2nd bag is fake
5 grams ... 3rd bag is fake
7 grams ... 4th bag is fake
11 grams ... 5th bag is fake
13 grams ... 6th bag is fake
17 grams ... 7th bag is fake
19 grams ... 8th bag is fake
23 grams ... 9th bag is fake
29 grams ... 10th bag is fake

hahah youre all dumb and im smart

You guys are retarded. Lift up each bag, feel which one of the ten is heaviest, this is the fake. The only way you would need to bother doing more than this is if you were to restate the problem as each bag both being sealed and containing an equal mass of coins.

>>1452475
That depends on how many coins are in each bag

>>1452461
by fake do you mean real?
who is dumb?

>>1452461

Why the hell do you think they have to be prime?

BUT WOT IF THE SACKS THEMSELVES ARE SIGNIFICANTLY HEAVY AND OF DIFFERENT MASSES, WITH MASSES THAT HAVE NO CORRELATION TO WHETHER OR NOT THE COINS THEY HOLD ARE FAKE OR NOT!?!?!?!?!

HAHAHAHAHHAHAHA YOU ARE ALL SCREWED

Better problem:

Now you have ten sacks, either all filled with gold or all filled with fakes. How to determine which sacks have fakes using only one weighing.

>>1452506

prime decomposition is unique. This is why you can inject NxNxN...(any finite number) into N

Okay sorry newfags... They dont have to be prime.. FU

>>1452485
it says there are equal amounts of gold coins in each bag

None of them are fake.

Fuck authority. I'd use the scale twice.

How about you don't use the scale at all? You just pick up the bags and see which one is heaviest.

>>1452580
this

>>1452461
>>1452461
>>1452461
I like this idea but you don't even need the primes. Use powers of 2. The result is in binary.

>>1452515

Where in this problem's solution do you need to take products?

just mix up all coins through all sacks and screw the counterfeits, no one will notice anyways.

>>1452627

Yes, and if you do it with powers of two you can solve this more general problem:

>>1452514

take a coin out of one of the bags and weigh it..

>>1452514
weigh all, if it weighs fake*10, all = fake
if it weighs real*10, all = real

srsly, that's not even remotely difficult.

>>1452627

wat, just do 1 from first bag, 2 from second, 3 from third etc.

result is in fukkin decimal.

>>1452647
>You have a scale.You can only use it once (read what it says only ONCE).
>(read what it says only ONCE).

>>1452647
won't work for any other number of fakebags, thou~

>>1452650
bitch, it works if there's only ONE fake bag.

>>1452638
So how do you determine which bags have fake gold?

>>1452658
1*real+2*real+3*real... etc,
the amount that you have, you find how much lacks from it.

there ya go :)

>>1452650

no shit.

1 coin from bag 1, 2 from bag 2, 3 from bag 3 etc all weighed at once. This number will be unique depending on which bag is fake.

The OP should have said whether he meant one of these or a scale which gives you a quantitative read out of the mass.

>>1451744
Open a bag and weigh 1 gold coin.

I go to someone who could identify a legitimate gold coin and ask him what they are