Q: Four teams are selling selling lemonade to customers walking out of a store. A total of 10 customers walk out of the store and randomly pick a team to buy lemonade from. What is the probability that all teams get at least one customer?

Probability Theory: The Logic of Science A: For simplicity, assume that the customers are walking out in a line and pick a team to buy lemonade from as shown in figure below.
The probability that a given team would get at least one customer is one minus the probability they get none. For a given customer and a given team, there is a $$\frac{4 - 1}{4} = \frac{3}{4}$$ probability that they will not connect. The probability that none of the 10 customers would pick a given team is $$\big(\frac{3}{4})^{10}$$.

Moving on, the probability that exactly one team would be without customers is $${4 \choose 1} \times\big(\frac{3}{4})^{10}$$, likewise the probability that exactly two and three teams would be without customers are $${4 \choose 2} \times\big(\frac{3}{4})^{10}$$ and $${4 \choose 3} \times\big(\frac{3}{4})^{10}$$ respectively. Thus the probability that all teams get at least one customer is one minus the sum of all the above probabilities

$$P(\text{at least 1 customer}) = 1 - \big(\frac{3}{4})^{10}\times(4 + 6 + 4) \approx 21\%$$

This problem is also a good candidate to try out some simulation and learn some R programming along the way. The following code simulates the above process and creates the same result.

Discovering Statistics Using R If you are looking to learn probability, some good books to own are shown below

Fifty Challenging Problems in Probability with Solutions (Dover Books on Mathematics) This book is a great compilation that covers quite a bit of puzzles. What I like about these puzzles are that they are all tractable and don't require too much advanced mathematics to solve.

Introduction to Algorithms This is a book on algorithms, some of them are probabilistic. But the book is a must have for students, job candidates even full time engineers & data scientists

Introduction to Probability Theory An Introduction to Probability Theory and Its Applications, Vol. 1, 3rd Edition The Probability Tutoring Book: An Intuitive Course for Engineers and Scientists (and Everyone Else!) Introduction to Probability, 2nd Edition The Mathematics of Poker
Good read. Overall Poker/Blackjack type card games are a good way to get introduced to probability theory

Bundle of Algorithms in Java, Third Edition, Parts 1-5: Fundamentals, Data Structures, Sorting, Searching, and Graph Algorithms (3rd Edition) (Pts. 1-5) An excellent resource (students/engineers/entrepreneurs) if you are looking for some code that you can take and implement directly on the job.

Understanding Probability: Chance Rules in Everyday Life A bit pricy when compared to the first one, but I like the look and feel of the text used. It is simple to read and understand which is vital especially if you are trying to get into the subject Data Mining: Practical Machine Learning Tools and Techniques, Third Edition (The Morgan Kaufmann Series in Data Management Systems) This one is a must have if you want to learn machine learning. The book is beautifully written and ideal for the engineer/student who doesn't want to get too much into the details of a machine learned approach but wants a working knowledge of it. There are some great examples and test data in the text book too. Discovering Statistics Using R This is a good book if you are new to statistics & probability while simultaneously getting started with a programming language. The book supports R and is written in a casual humorous way making it an easy read. Great for beginners. Some of the data on the companion website could be missing.

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### The Best Books to Learn Probability

If you are looking to buy some books in probability here are some of the best books to learn the art of Probability The Probability Tutoring Book: An Intuitive Course for Engineers and Scientists (and Everyone Else!) A good book for graduate level classes: has some practice problems in them which is a good thing. But that doesn't make this book any less of buy for the beginner. An Introduction to Probability Theory and Its Applications, Vol. 1, 3rd Edition This is a two volume book and the first volume is what will likely interest a beginner because it covers discrete probability. The book tends to treat probability as a theory on its own Discovering Statistics Using R This is a good book if you are new to statistics & probability while simultaneously getting started with a programming language. The book supports R and is written in a casual humorous way making it an easy read. Great for beginners. Some of the data on the companion website could be missing. Fifty Cha

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### The Best Books for Linear Algebra

The following are some good books to own in the area of Linear Algebra. Linear Algebra (2nd Edition) This is the gold standard for linear algebra at an undergraduate level. This book has been around for quite sometime a great book to own. Linear Algebra: A Modern Introduction Good book if you want to learn more on the subject of linear algebra however typos in the text could be a problem. Linear Algebra (Dover Books on Mathematics) An excellent book to own if you are looking to get into, or want to understand linear algebra. Please keep in mind that you need to have some basic mathematical background before you can use this book. Linear Algebra Done Right (Undergraduate Texts in Mathematics) A great book that exposes the method of proof as it used in Linear Algebra. This book is not for the beginner though. You do need some prior knowledge of the basics at least. It would be a good add-on to an existing course you are doing in Linear Algebra. Linear Algebra, 4th Ed