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甲有101個硬幣,乙有100個硬幣,兩人隨機撒在地面上,甲比乙正面朝上多的概率是多少?

2021-02-15知識

廢話不多說,直接上程式碼

import random import math sum_3 = 0 results = [] n = 10000000 for j in range ( n ): sum_1 = 0 sum_2 = 0 for i in range ( 101 ): s = random . randint ( 0 , 1 ) sum_1 += s for i in range ( 100 ): s = random . randint ( 0 , 1 ) sum_2 += s if sum_1 > sum_2 : sum_3 += 1 results . append ( sum_3 / ( j + 1 )) if ( j + 1 ) % 1000 == 0 : print ( sum_3 / ( j + 1 ))

跑了一千萬次,最後幾次結果是:

0.4998556133680208

0.49985622811405706

0.49985564225690277

0.4998554566369911

0.49985987197439485

0.49986148614861486

0.4998606

故甲有101個硬幣,乙有100個硬幣,兩人隨機撒在地面上,甲比乙正面朝上多的概率大約為

0.4998606

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2021.2.23 修改

記A為拋了101次硬幣,B為拋了100次硬幣,正面為z,反面為f。

P1 = A(z) > B(z)
P2 = A(f) > B(f)
P(z) = 1/2
P(f) = 1/2
-> P1 = P2
P3 = A(z) <= B(z)
P4 = A(f) <= B(f)

P3,P4交集為空 -> P1 + P2 = 1
P1 = P2 = 1/2