高中英语概率题!!! (有答案，求过程）

来源：百度知道 编辑：UC知道 时间：2024/06/28 06:18:52
determine the probability when two dice are rolled:
a) rolling doubles given that the sum is 8

Answer: 20%

please attach your answer with full procedures. thanks!

there are following situations

let's take a look at only one dice first

the possibilty of rolling each number equals to the others

so the possibility of rolling an expected number is one-sixth

then let's look at the situations

first situation:2+6

the possibility is:1/6*1/6*2=1/18

here we should multiply 2 for you can't decide which of the dices rolls a certain number

second situation:3+5

the possibility:1/6*1/6*2=1/18

third situation:4+4

the possibility:1/6*1/6=1/36

so the answer should be 5/36

not 20%

you've got a wrong answer

恩 同意楼上的~~~I havc the same answer with him.