Problem Solving
试题详情
题目：
A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster. If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?
选项:
A、0
B、1/9
C、2/9
D、1/3
E、1
答案:
C
提问：
请老师讲一下排列组合的题该如何做，经常做错。
1.什么时候用排列，什么时候用组合？
2.题目怎么问时用加法原则，题目怎么问时用乘法原则？
3. 这道题为什么不能是(1/3)^3
评分:
0
浏览:
4225
提问：
机经题：三角形三边，40,9和X，其中一个角大于90度，问X的可能值。答案有30,33,39,40,41.
思路：根据三角形三边的关系，31小于x小于49, 排除30。
若三角形有一个角是直角，当40,9为直角边时，x=41,当x>41时，40,9组成的角为钝角。排除41；
当x,9为直角边，x=根号（49*31）>35;所以x<35时，有一个角为钝角，选33.
评分:
0
浏览:
4229
提问：
A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster. If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?
0
1/9
2/9
1/3
1
评分:
0
浏览:
4216
