1. ## expectation

A boy and a girl arrive to a place randomly within 60 minutes. They are willing to wait for one another
for 20 mins. (If one of them,say the boy arrives and does not see the girl,he will expect that she will
come later and thus will wait for her.)
(1) What is the probability of their meeting at the place?
(2)What is the expectation of the waiting time for any one of them?

2. Originally Posted by yswong
A boy and a girl arrive to a place randomly within 60 minutes. They are willing to wait for one another
for 20 mins. (If one of them,say the boy arrives and does not see the girl,he will expect that she will
come later and thus will wait for her.)
(1) What is the probability of their meeting at the place?
(2)What is the expectation of the waiting time for any one of them?
You will find several questions of this type answered in detail in this subforum if you have a little patience to search for them.

3. Originally Posted by yswong
A boy and a girl arrive to a place randomly within 60 minutes. They are willing to wait for one another
for 20 mins. (If one of them,say the boy arrives and does not see the girl,he will expect that she will
come later and thus will wait for her.)
(1) What is the probability of their meeting at the place?
(2)What is the expectation of the waiting time for any one of them?
What exactly does the following mean: "A boy and a girl arrive to a place randomly within 60 minutes"?

CB

4. Originally Posted by mr fantastic
You will find several questions of this type answered in detail in this subforum if you have a little patience to search for them.

The 1st question is a simple geometric probability problem and the answer is 5/9.
However,the 2nd question is much more complicated and I have not got the answer yet.

5. Originally Posted by CaptainBlack
What exactly does the following mean: "A boy and a girl arrive to a place randomly within 60 minutes"?

CB
That means the boy and the girl will arrive separately at any time from 0 min.to 60 min.
( I am sorry for missing the word " separately".)