I'm really not understanding your calculations. At all.
DiMono wrote:
There are 47 ways for 4 of the outside squares to be mines.
I'm with you here.
For most of the other ways to do this, it's always some number * these 47. There are basically 2^12 outside combinations, so we're looking at 81 * 2^12 which is 4096 * 47 = 192512
But.... the total number of possible combinations of those 16 squares is 2^16 = 65536. You're saying there's 3x as many than that that actually work.
Yes, there are only 65536 total combinations, but this includes the mirror images. I'm going somewhere with this, don't worry.
The 65536 already counts mirror images, as it's counting EVERY possible combination. I'm really not following this.
Bah, let me just take a stab at it.
Number of bombs : number of combinations that work
0 : 0
1 : 0
2 : 0
3 : 0
4 : 47
5 : 472
6 : 1994
7 : 4836
8 : 7664
9 : 8496
10 : 6834
11 : 4052
12 : 1768
13 : 556
14 : 120
15 : 16
16 : 1
Number of bombs : chance of getting that number of bombs:
4 : (99/471 * 98/470 * 97/469 * 96/468) * (372/467 * 371/466 * 370/465 * 369/464 * 368/463 * 367/462 * 366/461 * 365/460 * 364/459 * 363/458 * 362/457 * 361/456)
That's long. Let's try to generalize.
x : (99!/(99-x)!) / (471!/(471-x)!) * (372!/(372-(16-x))!) / ((471-x)!/455!)
Hmm, I'm not sure if that's any easier.
denomiator will allways be 4533693136063779600000000000000000000000000, so I'll just list the numerators:
4 : 530347823907473880000000000000000000000
5 : 139565216817756310000000000000000000000
6 : 36240691659859375000000000000000000000
7 : 9284805301286286200000000000000000000
8 : 2346709032193236900000000000000000000
9 : 585069923094752290000000000000000000
10: 143869653220021040000000000000000000
11: 34889370944364775000000000000000000
12: 8343110443217665300000000000000000
13: 1967074819945628100000000000000000
14: 457211985176551460000000000000000
15: 104752072075490230000000000000000
16: 23653693694465535000000000000000
Now multiply each of those numerators by the # of combinations with that # of bombs:
4 : 24926347723651272000000000000000000000000
5 : 65874782337980979000000000000000000000000
6 : 72263939169759592000000000000000000000000
7 : 44901318437020480000000000000000000000000
8 : 17985178022728968000000000000000000000000
9 : 4970754066613015000000000000000000000000
10: 983205210105623840000000000000000000000
11: 141371731066566050000000000000000000000
12: 14750619263608832000000000000000000000
13: 1093693599889769300000000000000000000
14: 54865438221186171000000000000000000
15: 1676033153207843800000000000000000
16: 23653693694465535000000000000000
Add those all up, and put the denominator back in, and we have 232062797576915062579780335000000000000000/4533693136063779600000000000000000000000000
I'll reduce that to 5156951057264779168439563/100748736356972880000000000 before quitting.
Multiply that by the stuff in my first post - 312/480 * 380/479 * 379/478 * 378/477 * 377/476 * 376/475 * 375/474 * 374/473 * 373/472 = 125953458562065200000000/
1254310534691298400000000 = 314883646405163/3135776336728246.
So my answer is 5156951057264779168439563/100748736356972880000000000 * 314883646405163/3135776336728246.
____________________________
The greatness of a nation and its moral progress can be judged by the way it treats its animals.
--
Mahatma Gandhi