# A group of forty people contains thirty people who are in college and ten people who are not in college. Nine people are randomly selected. What is the probability that, of those nine people selected, …

Math 270A Name_________________________________
Fall 2018 – Worksheet 5
Directions: Print out this worksheet and write your answers directly onto it. Unless otherwise indicated,
you do not need to simplify your answers.
1. A group of forty people contains thirty people who are in college and ten people who are not in college.
Nine people are randomly selected. What is the probability that, of those nine people selected, …
a. exactly seven are in college? c. at least one is in college?
b. all nine are in college? d. exactly four or exactly five are in college?
2. A fair coin is flipped 15 times. What is the probability of getting…
a. at least one head? b. exactly five heads?
3. In this problem, simplify your answers to get an integer. And note that you are being asked for “how
many”, not for probability. How many 9-bit strings are there…
a. that start with 11 or end with
001?
b. that contain exactly two 1’s? c. that end with 1111 and contain
exactly seven 1’s ?
4. Without using a calculator, evaluate (
10
4
) to get an integer. Show all your work.