作业帮求助一道gre数学题,请不会的千万不要乱回答,·if an integer is randomly selected from all positive 2-digit integers,what is the probability that the integer chosen has (a) a 4 in the tens place(b) at least one 4 in the tens place or th
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求助一道gre数学题,请不会的千万不要乱回答,·if an integer is randomly selected from all positive 2-digit integers,what is the probability that the integer chosen has (a) a 4 in the tens place(b) at least one 4 in the tens place or th
求助一道gre数学题,请不会的千万不要乱回答,·
if an integer is randomly selected from all positive 2-digit integers,what is the probability that the integer chosen has
(a) a 4 in the tens place
(b) at least one 4 in the tens place or the units place?
(c)no 4 in either place?
求助一道gre数学题,请不会的千万不要乱回答,·if an integer is randomly selected from all positive 2-digit integers,what is the probability that the integer chosen has (a) a 4 in the tens place(b) at least one 4 in the tens place or th
在所有正二位整数中随机取一个,以下各条件的几率
正二位整数：10 99 一共90个
a) 十位数为4
40 49 10个
几率：10/90 = 1/9
b) 个位或十位,至少有一个是4
个位：14,24,.94 9个
扣掉 44重复 则 9 + 10 - 1 = 18个
几率：18/90 = 1/5
c) 两位都不是 4 （即 b 以外的）
1 - 1/5 = 4/5
为什么是英文
题干含义：从两位正整数中随机的选取一个整数，求概率 a) 4在十位 b) 至少一个4在十位或个位 C）任何位置没有4