# What's the effect of having more than one scrap recovery arm?

How much scrap do I get with two Scrap Recovery Arm augments installed? 110%, 120%, 121%, or some number that doesn't make any sense?

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I don't know if it's 120% or 121%, but they do stack, so it won't be 110%. – Samthere Sep 27 '12 at 13:58
they definitely stack, but I can't tell either if its 120 or 121 since the difference is so small and the value is random each time – l I Sep 27 '12 at 14:07
It might be easier to find out by getting 2-3 of another stackable augment with a fixed value (e.g. FTL recharge boost) and seeing if that is additive or multiplicative. – user2640 Sep 27 '12 at 14:19
frankly I don't think the difference matters. Assuming you get it really early on in the game, and the number of scrap events there are, (most of which will be below 100 so it probably rounds off anyway), maybe it'll make a scrap difference of 10-20, tops? – l I Sep 27 '12 at 14:49
@JoeWreschnig That's not a guarantee it would be the same for the recovery arm though. – Hackworth Sep 27 '12 at 17:26

After reading Hackworth's table, I decided to test a bit. I got 2 scrap recovery arms, and started writing down every time I received some scrap. I wrote down both the amount I was promised and the actual amount I received. Then I put it in Excel, and compared it to 3 lists corresponding to Hackworth's A, B and C (additive, multiplicative and independently rounded, respectively). It turns out the formula (at least for 2 arms, I assume it's the same for 3) is: Scrap received = floor(Scrap promised * (1 + 10% / (number of arms) ) or: Sr = floor(Sp*(1+0,1*n))

Documentation: Excel sheet with data (I also have screenshots from 3 different amounts, but as a new user I'm not allowed to post more than 2 links in one post)

tl;dr: The arms stack additively rounded down

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Hi Jonas, and welcome to Arqade! Nice answer! My only suggestion would be to load your data into a Google Docs spreadsheet so that it's more accessible to the other members. – MBraedley Sep 29 '12 at 10:26
+1 for SCIENCE!! (science gets you far here, by the way. good start) – Ender Sep 30 '12 at 18:10
@MBraedley The Google Docs Viewer can be used for a rough glance at the spreadsheet. – Schism Oct 1 '12 at 6:16
Shouldn't that be "10% * (number of arms)"? – Brilliand Apr 29 '14 at 15:56

I can't answer the question definitely, but I know that the scrap recovery arms do stack, and I have set up a table that lets anyone with 2 or 3 scrap recovery arms quickly decide which stacking method is being used.

There are 3 possible ways to calculate the bonus scrap:

A. The 10% bonus stacks additively, giving a total of 120% (130%), rounded down.

B. The 10% bonus stacks multiplicatively, giving a total of 121% (133.1%), rounded down.

C. The 10% bonus is calculated and rounded independently for each arm, and added up after rounding each bonus scrap amount individually.

Putting it into a spreadsheet for base scrap 1-100 gives the following results for total scrap. If you ever get to play with 2 or 3 arms, you can compare your actual results against this table, and if you get e.g. 58 or 59 base scrap at 2 arms, you can definitely tell which calculation method is being used in the game. Either way, as already pointed out in the comments, the difference is quite small in practice and should probably not be a deciding factor on the question whether or not to get a second or even third scrap recovery arm over a different kind of augmentation.

```Scrap   2 arms          3 arms
A   B   C       A   B   C
1       1   1   1       1   1   1
2       2   2   2       2   2   2
3       3   3   3       3   3   3
4       4   4   4       5   5   4
5       6   6   5       6   6   5
6       7   7   6       7   7   6
7       8   8   7       9   9   7
8       9   9   8       10  10  8
9       10  10  9       11  11  9
10      12  12  12      13  13  13
11      13  13  13      14  14  14
12      14  14  14      15  15  15
13      15  15  15      16  17  16
14      16  16  16      18  18  17
15      18  18  17      19  19  18
16      19  19  18      20  21  19
17      20  20  19      22  22  20
18      21  21  20      23  23  21
19      22  22  21      24  25  22
20      24  24  24      26  26  26
21      25  25  25      27  27  27
22      26  26  26      28  29  28
23      27  27  27      29  30  29
24      28  29  28      31  31  30
25      30  30  29      32  33  31
26      31  31  30      33  34  32
27      32  32  31      35  35  33
28      33  33  32      36  37  34
29      34  35  33      37  38  35
30      36  36  36      39  39  39
31      37  37  37      40  41  40
32      38  38  38      41  42  41
33      39  39  39      42  43  42
34      40  41  40      44  45  43
35      42  42  41      45  46  44
36      43  43  42      46  47  45
37      44  44  43      48  49  46
38      45  45  44      49  50  47
39      46  47  45      50  51  48
40      48  48  48      52  53  52
41      49  49  49      53  54  53
42      50  50  50      54  55  54
43      51  52  51      55  57  55
44      52  53  52      57  58  56
45      54  54  53      58  59  57
46      55  55  54      59  61  58
47      56  56  55      61  62  59
48      57  58  56      62  63  60
49      58  59  57      63  65  61
50      60  60  60      65  66  65
51      61  61  61      66  67  66
52      62  62  62      67  69  67
53      63  64  63      68  70  68
54      64  65  64      70  71  69
55      66  66  65      71  73  70
56      67  67  66      72  74  71
57      68  68  67      74  75  72
58      69  70  68      75  77  73
59      70  71  69      76  78  74
60      72  72  72      78  79  78
61      73  73  73      79  81  79
62      74  75  74      80  82  80
63      75  76  75      81  83  81
64      76  77  76      83  85  82
65      78  78  77      84  86  83
66      79  79  78      85  87  84
67      80  81  79      87  89  85
68      81  82  80      88  90  86
69      82  83  81      89  91  87
70      84  84  84      91  93  91
71      85  85  85      92  94  92
72      86  87  86      93  95  93
73      87  88  87      94  97  94
74      88  89  88      96  98  95
75      90  90  89      97  99  96
76      91  91  90      98  101 97
77      92  93  91      100 102 98
78      93  94  92      101 103 99
79      94  95  93      102 105 100
80      96  96  96      104 106 104
81      97  98  97      105 107 105
82      98  99  98      106 109 106
83      99  100 99      107 110 107
84      100 101 100     109 111 108
85      102 102 101     110 113 109
86      103 104 102     111 114 110
87      104 105 103     113 115 111
88      105 106 104     114 117 112
89      106 107 105     115 118 113
90      108 108 108     117 119 117
91      109 110 109     118 121 118
92      110 111 110     119 122 119
93      111 112 111     120 123 120
94      112 113 112     122 125 121
95      114 114 113     123 126 122
96      115 116 114     124 127 123
97      116 117 115     126 129 124
98      117 118 116     127 130 125
99      118 119 117     128 131 126
100     120 121 120     130 133 130

```
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