**Degree: B.S., Mathematics and Computer Science; Ph.D., Theoretical Computer Science****Position: Software Engineer****Company: Google Inc.**

What would a search engine find if you input the terms “path to a great career”? For David Arthur, mathematics and computer science was the correct search result.

David is a software engineer at Google Inc. One of the world’s top software companies, Google is consistently ranked as one of the best places to work in the world. David works mainly on the Google advertising system, which involves tasks such as improving the infrastructure, adding new features, and improving algorithms.

“Math comes up again and again at Google,” says David. Probability theory, statistical models, and algorithms help to ensure the accuracy of Google searches, determine optimal ad placement, and analyze changes to the system. “We decide what ads to show and where to show them based on a sophisticated auction that balances Google’s revenue, user happiness, and advertiser happiness,” says David.

Originally from Toronto, David received his B.S. in mathematics and computer science from Duke University and his PhD in theoretical computer science from Stanford University. Though David’s Ph.D. is in computer science, he says his Ph.D. thesis was “100 pages of mathematical proofs, with no computers anywhere to be seen!”

David’s thesis is only one example of how the worlds of mathematics and computer science intersect. “If you look at algorithms, complexity theory, cryptography, or even machine learning, you’ll see fields that could have just as easily been called math as computer science,” says David. “Computer scientists got there first, but the questions they ask are mathematical in nature, and only math can solve them.”

As a high school student, David became hooked on math by participating in mathematics competitions. “They were more interesting and more beautiful than what I had learned in school, and I liked the competitive aspect,” says David.

In 1999 and 2000, David was a member of the Canadian student team to the International Mathematical Olympiad (IMO). In 2000, David received a gold medal and was only 4 points away from a perfect score. Participating in the IMO was an unforgettable experience for David. “The IMO was a chance to see something beautiful, to meet people from across the world, and to excel at something I cared about,” he says. Today, David carries on supporting Canada at the IMO, having acted as the Deputy Team Leader for the 2009 and 2011 events. “It is no less inspiring to meet the world’s best mathematicians now than it was ten years ago,” says David.