Help me calculate the crafting chance

Someone help me calculate the chance to get both of these gold line if i craft with 2 other trash gun :

 

1/28 * 100%

For example:
Chance of getting first random stat you need is 2/8, because you have 2 atts you like out of 8.

Chance of getting the second one is 1/7, because out of remaining 7, you have only one you need. The first one was taken on step 1.

So 2/8 * 1/7 = 1/4 * 1/7 = 1/28 (*100%)

Or, you can just calculate number of combinations
8 choose 2 = 28. Since you would only accept 1 combination out of 28 possible, it is 1/28th

Should you placw 3 blue items like that, chances would be 3/8 * 2/7 = 3/28

In case of 4 items, - 4/8 * 3/7 = 3 / 14

Generic formula would be:

(G choose n) / (P choose n), where
n - is number of lines going into crafted item
G - total number of good stats in 4 items
P - total number of stats in for items.

Formula for N choose K is (N!) / (K! * (N - K)!)
N! = 1 * 2 * ... * (N-1) * N

Example with purple items. You have 2/3, 2/3, 1/3, 0/3 purple items, where the first number is golden lines. Your chaces:
G = 2 + 2 + 1 = 5 (golden lines)
P = 3 + 3 + 3 + 3 = 12 (total number of lines)
n = 3 (go into legendary)
(5 choose 3) / (12 choose 3) = 10 / 220 * 100% = 1/22 * 100% = ~4.5454%

This does not take into account a possibility of last random attrubute being good. That chance is marginal, however, so could be ignored

 

In case you were wondering... That is about 7%

 

Actually it is ~3.57%

 

Thank for the reply guys
Especially thank for your formula serbastian, it's very helpful xD

 

If you want to save time doing the calculations, you can also use the probability table I posted here. Good luck!

 

wow, amazing! ty alot for that table

 

Long story short, it takes a lot of gold, junk items, and luck (which all adds up to a lot of time), but it can be done.

 

2/28 is about 7%... Yes?

 

Yes, but the desired outcome has a 1/28 chance, not a 2/28 (1/14) chance.

Bottom line, unless you like math, just use Armando's table.

 

I was counting values not outcomes I think. Stupid mistake. I think I'll just use Armando's table...

 

Hey there heroes,

Thank you for your answers
@Yamaac_chocobo , was your question fully answered or do you have anything more to ask?

Cheers,

 

I have no more thing to ask, you can close now

 

As demanded,

CLOSED​