Thread: Combinations/Probability...please check my work

A) In a board game, there are tiles with letters on one side. There are 56 with consonants and 42 with vowels. A player chooses 7 tiles to start. What is the probability of choosing 4 consonants and 3 vowels?

Is it ((56C4)(42C3))/(98C7)?

B) You arrange five books (A, B, C, D, E) on a shelf. What is the probability that book E is last?
I know intuitively it is 1/5, but I need to use combinations. How do I do so?

Originally Posted by twittytwitter

A) In a board game, there are tiles with letters on one side. There are 56 with consonants and 42 with vowels. A player chooses 7 tiles to start. What is the probability of choosing 4 consonants and 3 vowels? Is it ((56C4)(42C3))/(98C7)

B) You arrange five books (A, B, C, D, E) on a shelf. What is the probability that book E is last?
I know intuitively it is 1/5, but I need to use combinations. How do I do so?

Your answer to part A is correct.

For part B. You need permutations.
There are ways to arrange the five books.
E will be the last book in of those arrangements.
So your intuition is correct.