[engineer question] coins

[martyr]

each bad coin is exactly 1mg underweight == .99g

edit, out of curiosity, what would you do with a bucket of water, if you had one?

[Strygun]

depending on the alloy, one could theoretically take a sharp object and scratch each of the coins. if the coin does not scratch, it is the correct coin. if it scratches, more than likely it's a bad coin.

[EineBeBoP]

I'd take all the coins to your local vendor, see if he accepts them.
If he rejects one, thats the bad coin. If not, who gives a fuck as nobody will know the differance!

[Jaged]

How much is a faulty coin's weight different from a normal coin's weight.

Assuming that all faulty coins weigh the same:

If you take 1 coin from the 1st machine, 2 from the 2nd, 3 from the 3rd, 4 from the 4th ect. Weigh the entire pile. If all the machines were working you should get 55g. Lets say that faulty coins all weigh 1/2g. If machine 1 was busted there would be 1 faulty coin. The total weight would be 54 1/2g. If machine 2 is busted there are 2 faulty coins in the mix. The total weight would be 54g. And so on....


Edit: I diddn't see maryter's post saying how much the faulty coins weigh. My solution still works for his faulty coin weight though.

[Indecisive]

...There is no solution O_o?

[Strygun]

what is the area of the coins? ( A = pi*(R*R) )

[Indecisive]

all pysical aspects are the same stry, volume would include the diameter of the coin, and the thickness.

[Jaged]

I just posted the answer guys, you can stop debating I belive.

[Strygun]

I know, I need to know for another math equation I'm working up

[Baneblade]

Oh that is easy then. Simply put them all one by one on the scale and keep adjusting the weights till you run across one that doesn't add up.

Don't take them off the scale, just stack em.

[Strygun]

Originally Posted by Sobekeus

Oh that is easy then. Simply put them all one by one on the scale and keep adjusting the weights till you run across one that doesn't add up.

Don't take them off the scale, just stack em.

that would be finding the weight of each coin, which you can't do.

[Indecisive]

you may use a scale to weigh a mass only once.

^

[Baneblade]

Fine, take 100 from each machine and lift em. It should be obvious which is lighter.

[Strygun]

Originally Posted by Sobekeus

Fine, take 100 from each machine and lift em. It should be obvious which is lighter.

doubt it, that would mean one pile is only 1g less than the others, and that's hard to detect.

[martyr]

Originally Posted by Strygun

depending on the alloy, one could theoretically take a sharp object and scratch each of the coins. if the coin does not scratch, it is the correct coin. if it scratches, more than likely it's a bad coin.

the rockwell measurements are identical