Tree diagram probability

[Clay]

Hi, I'm having some trouble with these two questions, any help would be appreciated, answer or otherwise.

 

[tkhunny]

Give a go for Part B, please. Show us anything to work with in helping you most effectively.

 

[R.M.]

For part A, how many ways can 2 names be chosen? How many ways can "Colin - Other" be chosen? How about "Other - Colin", or "Colin - Colin"? Answer these questions, and you can piece together your probability.

 

[pka]

This is a pairing of two classic types of the same problem.
Problem A has \(100\) possible outcomes: \(10\times 10\) ordered pairs.
Problem B has \(\dbinom{10}{2}=45\) possible outcomes: that is choosing two from ten.
PART A: Of the one hundred ordered pairs, there are \(19\) pairs that contain Colin at least once.
PART B: Of the forty-five two-selections, Colin is in nine of the selections.
Clay, you need to use the above and post your results. Please, please do it.