Ask The Wizard #317
Golf Digest claims that if four amateur golfers play a round that the probability that two get a hole-in-one on the same hole are 1 in 26,000,000. Do you agree with that figure?
No, I don't.
I will have to take on faith their statistic that for an amateur golfer, the probability of a hole-in-one are 1 in 12,500 per hole.
However, almost all hole-in-ones are achieved on par-3 holes. The typical course will have four such holes. So, the probability of a hole-in-one on a par 3 hole is (1/12500) × (4/18) = 1 in 2,778.
That said, the probability that exactly two golfers out of four get a hole-in-one on a par 3 hole is combin(4,2) × (1/12500)2 × (12449/12500)2 = 1 in 1,286,935.
Assuming four par-3 holes in a round, the probability of two hole-in-ones in the same hole are 4 × (1/1,286,935) = 1 in 321,734.
Where Golf Digest seems to have gone wrong is in assuming every hole has the same probability of a hole in one.
This question is raised and discussed in my forum at Wizard of Vegas.
A number of sports books, like the MGM in New Jersey, are offering a truly free bet — if the bet looses, they refund in CASH you can then withdraw. Like a 100% loss rebate for slots, but applied to sports betting. What kind of bet should I make under this promotion?
With any free-roll like this, you should shoot for the moon. If they allow parlays, then parlay bet as much as they allow under this promotion and parlay enough events to get up to whatever their maximum payout is, which in Las Vegas is typically around $100,000.
If you have to bet on a single event, then find the biggest long-shot you can.
As an example of why this strategy is best, consider the same promotion in double-zero roulette with a $100 bet. If you make an even-money bet, then the expected amount you'll get back is (18/38)×$200 + (20/38)×$100 = $147.37. However, if you bet on a single number, then you can expect to get back (1/38)×$3600 + (37/38)×$100 = $192.11.
I found a blackjack dealer who exposes his hole card when peeking for blackjack. He offers insurance after peeking. So, when the dealer has an ace up and I can see a 10, I take insurance. How much does this reduce the house edge of the overall game?
Let's assume six decks. The probability of the up card being an ace is 1/13. Next, the probability the hole card is a 10-point card is 96/311. So, this opportunity will occur 2.37% of hands.
The insurance bet I assume will be half a unit and insurance pays 2 to 1. So, every time this happens, you can expect to gain a unit. Since it happens with probability 2.37% of the time, that is what it is worth to you. Subtract the house edge under whatever the blackjack rules are to get the overall player advantage of the game.
Let's say a dealer has chips of every denomination evenly divisible by $1. You buy in at the table for $10. How many different ways can the dealer give change for the $10? How about for other buy-in amounts?
There are 42 ways the dealer could break down $10. Here they are:
9,1
8,2
8,1,1
7,3
7,2,1
7,1,1,1
6,4
6,3,1
6,2,2
6,2,1,1
6,1,1,1,1
5,5
5,4,1
5,3,2
5,3,1,1
5,2,2,1
5,2,1,1,1
5,1,1,1,1,1
4,4,2
4,4,1,1
4,3,3
4,3,2,1
4,3,1,1,1
4,2,2,2
4,2,2,1,1
4,2,1,1,1,1
4,1,1,1,1,1,1
3,3,3,1
3,3,2,2
3,3,2,1,1
3,3,1,1,1,1
3,2,2,2,1
3,2,2,1,1,1
3,2,1,1,1,1,1
3,1,1,1,1,1,1,1
2,2,2,2,2
2,2,2,2,1,1
2,2,2,1,1,1,1
2,2,1,1,1,1,1,1
2,1,1,1,1,1,1,1,1
1,1,1,1,1,1,1,1,1,1
Mathematicians call these partitions. Here are the number of partitions for starting quantities up to 405, which is as high as my computer can calculate (2^64).
Common Birthday to 2+ People
Initial Quantity |
Total Partitions |
---|---|
1 | 1 |
2 | 2 |
3 | 3 |
4 | 5 |
5 | 7 |
6 | 11 |
7 | 15 |
8 | 22 |
9 | 30 |
10 | 42 |
11 | 56 |
12 | 77 |
13 | 101 |
14 | 135 |
15 | 176 |
16 | 231 |
17 | 297 |
18 | 385 |
19 | 490 |
20 | 627 |
21 | 792 |
22 | 1002 |
23 | 1255 |
24 | 1575 |
25 | 1958 |
26 | 2436 |
27 | 3010 |
28 | 3718 |
29 | 4565 |
30 | 5604 |
31 | 6842 |
32 | 8349 |
33 | 10143 |
34 | 12310 |
35 | 14883 |
36 | 17977 |
37 | 21637 |
38 | 26015 |
39 | 31185 |
40 | 37338 |
41 | 44583 |
42 | 53174 |
43 | 63261 |
44 | 75175 |
45 | 89134 |
46 | 105558 |
47 | 124754 |
48 | 147273 |
49 | 173525 |
50 | 204226 |
51 | 239943 |
52 | 281589 |
53 | 329931 |
54 | 386155 |
55 | 451276 |
56 | 526823 |
57 | 614154 |
58 | 715220 |
59 | 831820 |
60 | 966467 |
61 | 1121505 |
62 | 1300156 |
63 | 1505499 |
64 | 1741630 |
65 | 2012558 |
66 | 2323520 |
67 | 2679689 |
68 | 3087735 |
69 | 3554345 |
70 | 4087968 |
71 | 4697205 |
72 | 5392783 |
73 | 6185689 |
74 | 7089500 |
75 | 8118264 |
76 | 9289091 |
77 | 10619863 |
78 | 12132164 |
79 | 13848650 |
80 | 15796476 |
81 | 18004327 |
82 | 20506255 |
83 | 23338469 |
84 | 26543660 |
85 | 30167357 |
86 | 34262962 |
87 | 38887673 |
88 | 44108109 |
89 | 49995925 |
90 | 56634173 |
91 | 64112359 |
92 | 72533807 |
93 | 82010177 |
94 | 92669720 |
95 | 104651419 |
96 | 118114304 |
97 | 133230930 |
98 | 150198136 |
99 | 169229875 |
100 | 190569292 |
101 | 214481126 |
102 | 241265379 |
103 | 271248950 |
104 | 304801365 |
105 | 342325709 |
106 | 384276336 |
107 | 431149389 |
108 | 483502844 |
109 | 541946240 |
110 | 607163746 |
111 | 679903203 |
112 | 761002156 |
113 | 851376628 |
114 | 952050665 |
115 | 1064144451 |
116 | 1188908248 |
117 | 1327710076 |
118 | 1482074143 |
119 | 1653668665 |
120 | 1844349560 |
121 | 2056148051 |
122 | 2291320912 |
123 | 2552338241 |
124 | 2841940500 |
125 | 3163127352 |
126 | 3519222692 |
127 | 3913864295 |
128 | 4351078600 |
129 | 4835271870 |
130 | 5371315400 |
131 | 5964539504 |
132 | 6620830889 |
133 | 7346629512 |
134 | 8149040695 |
135 | 9035836076 |
136 | 10015581680 |
137 | 11097645016 |
138 | 12292341831 |
139 | 13610949895 |
140 | 15065878135 |
141 | 16670689208 |
142 | 18440293320 |
143 | 20390982757 |
144 | 22540654445 |
145 | 24908858009 |
146 | 27517052599 |
147 | 30388671978 |
148 | 33549419497 |
149 | 37027355200 |
150 | 40853235313 |
151 | 45060624582 |
152 | 49686288421 |
153 | 54770336324 |
154 | 60356673280 |
155 | 66493182097 |
156 | 73232243759 |
157 | 80630964769 |
158 | 88751778802 |
159 | 97662728555 |
160 | 107438159466 |
161 | 118159068427 |
162 | 129913904637 |
163 | 142798995930 |
164 | 156919475295 |
165 | 172389800255 |
166 | 189334822579 |
167 | 207890420102 |
168 | 228204732751 |
169 | 250438925115 |
170 | 274768617130 |
171 | 301384802048 |
172 | 330495499613 |
173 | 362326859895 |
174 | 397125074750 |
175 | 435157697830 |
176 | 476715857290 |
177 | 522115831195 |
178 | 571701605655 |
179 | 625846753120 |
180 | 684957390936 |
181 | 749474411781 |
182 | 819876908323 |
183 | 896684817527 |
184 | 980462880430 |
185 | 1071823774337 |
186 | 1171432692373 |
187 | 1280011042268 |
188 | 1398341745571 |
189 | 1527273599625 |
190 | 1667727404093 |
191 | 1820701100652 |
192 | 1987276856363 |
193 | 2168627105469 |
194 | 2366022741845 |
195 | 2580840212973 |
196 | 2814570987591 |
197 | 3068829878530 |
198 | 3345365983698 |
199 | 3646072432125 |
200 | 3972999029388 |
201 | 4328363658647 |
202 | 4714566886083 |
203 | 5134205287973 |
204 | 5590088317495 |
205 | 6085253859260 |
206 | 6622987708040 |
207 | 7206841706490 |
208 | 7840656226137 |
209 | 8528581302375 |
210 | 9275102575355 |
211 | 10085065885767 |
212 | 10963707205259 |
213 | 11916681236278 |
214 | 12950095925895 |
215 | 14070545699287 |
216 | 15285151248481 |
217 | 16601598107914 |
218 | 18028182516671 |
219 | 19573856161145 |
220 | 21248279009367 |
221 | 23061871173849 |
222 | 25025873760111 |
223 | 27152408925615 |
224 | 29454549941750 |
225 | 31946390696157 |
226 | 34643126322519 |
227 | 37561133582570 |
228 | 40718063627362 |
229 | 44132934884255 |
230 | 47826239745920 |
231 | 51820051838712 |
232 | 56138148670947 |
233 | 60806135438329 |
234 | 65851585970275 |
235 | 71304185514919 |
236 | 77195892663512 |
237 | 83561103925871 |
238 | 90436839668817 |
239 | 97862933703585 |
240 | 105882246722733 |
241 | 114540884553038 |
242 | 123888443077259 |
243 | 133978259344888 |
244 | 144867692496445 |
245 | 156618412527946 |
246 | 169296722391554 |
247 | 182973889854026 |
248 | 197726516681672 |
249 | 213636919820625 |
250 | 230793554364681 |
251 | 249291451168559 |
252 | 269232701252579 |
253 | 290726957916112 |
254 | 313891991306665 |
255 | 338854264248680 |
256 | 365749566870782 |
257 | 394723676655357 |
258 | 425933084409356 |
259 | 459545750448675 |
260 | 495741934760846 |
261 | 534715062908609 |
262 | 576672674947168 |
263 | 621837416509615 |
264 | 670448123060170 |
265 | 722760953690372 |
266 | 779050629562167 |
267 | 839611730366814 |
268 | 904760108316360 |
269 | 974834369944625 |
270 | 1050197489931117 |
271 | 1131238503938606 |
272 | 1218374349844333 |
273 | 1312051800816215 |
274 | 1412749565173450 |
275 | 1520980492851175 |
276 | 1637293969337171 |
277 | 1762278433057269 |
278 | 1896564103591584 |
279 | 2040825852575075 |
280 | 2195786311682516 |
281 | 2362219145337711 |
282 | 2540952590045698 |
283 | 2732873183547535 |
284 | 2938929793929555 |
285 | 3160137867148997 |
286 | 3397584011986773 |
287 | 3652430836071053 |
288 | 3925922161489422 |
289 | 4219388528587095 |
290 | 4534253126900886 |
291 | 4872038056472084 |
292 | 5234371069753672 |
293 | 5622992691950605 |
294 | 6039763882095515 |
295 | 6486674127079088 |
296 | 6965850144195831 |
297 | 7479565078510584 |
298 | 8030248384943040 |
299 | 8620496275465025 |
300 | 9253082936723602 |
301 | 9930972392403501 |
302 | 10657331232548839 |
303 | 11435542077822104 |
304 | 12269218019229465 |
305 | 13162217895057704 |
306 | 14118662665280005 |
307 | 15142952738857194 |
308 | 16239786535829663 |
309 | 17414180133147295 |
310 | 18671488299600364 |
311 | 20017426762576945 |
312 | 21458096037352891 |
313 | 23000006655487337 |
314 | 24650106150830490 |
315 | 26415807633566326 |
316 | 28305020340996003 |
317 | 30326181989842964 |
318 | 32488293351466654 |
319 | 34800954869440830 |
320 | 37274405776748077 |
321 | 39919565526999991 |
322 | 42748078035954696 |
323 | 45772358543578028 |
324 | 49005643635237875 |
325 | 52462044228828641 |
326 | 56156602112874289 |
327 | 60105349839666544 |
328 | 64325374609114550 |
329 | 68834885946073850 |
330 | 73653287861850339 |
331 | 78801255302666615 |
332 | 84300815636225119 |
333 | 90175434980549623 |
334 | 96450110192202760 |
335 | 103151466321735325 |
336 | 110307860425292772 |
337 | 117949491546113972 |
338 | 126108517833796355 |
339 | 134819180623301520 |
340 | 144117936527873832 |
341 | 154043597379576030 |
342 | 164637479165761044 |
343 | 175943559810422753 |
344 | 188008647052292980 |
345 | 200882556287683159 |
346 | 214618299743286299 |
347 | 229272286871217150 |
348 | 244904537455382406 |
349 | 261578907351144125 |
350 | 279363328483702152 |
351 | 298330063062758076 |
352 | 318555973788329084 |
353 | 340122810048577428 |
354 | 363117512048110005 |
355 | 387632532919029223 |
356 | 413766180933342362 |
357 | 441622981929358437 |
358 | 471314064268398780 |
359 | 502957566506000020 |
360 | 536679070310691121 |
361 | 572612058898037559 |
362 | 610898403751884101 |
363 | 651688879997206959 |
364 | 695143713458946040 |
365 | 741433159884081684 |
366 | 790738119649411319 |
367 | 843250788562528427 |
368 | 899175348396088349 |
369 | 958728697912338045 |
370 | 1022141228367345362 |
371 | 1089657644424399782 |
372 | 1161537834849962850 |
373 | 1238057794119125085 |
374 | 1319510599727473500 |
375 | 1406207446561484054 |
376 | 1498478743590581081 |
377 | 1596675274490756791 |
378 | 1701169427975813525 |
379 | 1812356499739472950 |
380 | 1930656072350465812 |
381 | 2056513475336633805 |
382 | 2190401332423765131 |
383 | 2332821198543892336 |
384 | 2484305294265418180 |
385 | 2645418340688763701 |
386 | 2816759503217942792 |
387 | 2998964447736452194 |
388 | 3192707518433532826 |
389 | 3398704041358160275 |
390 | 3617712763867604423 |
391 | 3850538434667429186 |
392 | 4098034535626594791 |
393 | 4361106170762284114 |
394 | 4640713124699623515 |
395 | 4937873096788191655 |
396 | 5253665124416975163 |
397 | 5589233202595404488 |
398 | 5945790114707874597 |
399 | 6324621482504294325 |
400 | 6727090051741041926 |
401 | 7154640222653942321 |
402 | 7608802843339879269 |
403 | 8091200276484465581 |
404 | 8603551759348655060 |
405 | 9147679068859117602 |
This question is raised and discussed in my forum at Wizard of Vegas.