Question

概率问题 急求！！！ 在线等 - -

小明中午吃挂面的几率是70% 而中午吃挂面同时晚饭吃烧饼的几率为56% 问 小明晚饭吃烧饼的几率为多少？ 又小明中饭不吃挂面晚饭不吃烧饼的几率为多少？
Harry always has lunch and dinner. He likes Italian food.

The probability that Harry has pasta for lunch is 0.7

The probability that Harry has pasta for lunch and has pizza for dinner is 0.56

Given that the events "Harry has pasta for lunch" and "Harry has pizza for dinner" are independent, find

the probability that Harry has pizza for dinner,

the probability that Harry does not have pasta for lunch and does not have pizza for dinner..

英文原版。对照看一下 可能翻译有误

Answer 1

令 A = 中午吃挂面事件 B=晚饭吃烧饼事件
那么A、B可以认为是独立的
中午吃挂面同时晚饭吃烧饼事件 = AB
所以 P(AB)=P(A)P(B) = 0.7P(B)=0.56,得P(B)=0.8 =80%
小明中饭不吃挂面晚饭不吃烧饼概率 = (1-P(A))(1-P(B))=0.3 * 0.2 = 0.06 =6%
所以
小明晚饭吃烧饼的几率为多少80%
小明中饭不吃挂面晚饭不吃烧饼概率 6%

Answer 2

小明晚饭吃烧饼的概率是0.8，即0.56/0.7
小明中饭不吃挂面晚饭不吃烧饼的几率=（1-0.7）*（1-0.8）=0.06

Answer 3

画个圆形 标注出来几率不就知道啦
吃烧饼的几率就是 吃挂面的几率减去又吃挂面又吃烧饼的几率 70%-56% 14%嘛
不吃挂面又不吃烧饼的几率就是 所有的几率中 减去要吃挂面的几率70% 也就是
100%-70% 等于30%嘛。。。。
这么简单的
画个图 一般都能解答出很多这种类型的题目
图解法