Hu Yoshida

How Do You Explain Prime Numbers to a Three-Year-Old?

Blog Post created by Hu Yoshida Employee on Jul 6, 2015

Yesterday, Sharon Crost, the head of our social media team, and I took our former intern, Chloe Bertao to lunch to thank her for her contributions to our social media team, celebrate her graduation from UC Santa Barbara, and her new job with one of our customers up the street from us.  We had tried to hire her, but we could not close on it in time. However, we were delighted to see her being hired by one of the most innovative companies in the world.




During lunch, I asked her what were some of the most interesting interview questions that she experienced during her hiring process. The one she found most interesting was: “How do you explain prime numbers to a three-year-old?


I asked her what her answer was, but she asked me what our answers would be first.  I fumbled around thinking back to my school days when I learned about prime numbers. A prime number is a number that can only be divided by itself and one. Then I thought about what three-year-olds know about numbers. I had raised two children and will soon be a grandfather of a three-year-old, so I have some experience with three-year-olds. I can also remember some of the things I knew at that age. I don’t think I could count to 10, much less do division at that age. I was stumped.


Sharon did a lot better; she thought of using chocolate chip cookies and having the child try to cut up the cookies into pieces with equal amounts of chips in each piece. Then Chloe explained how she would use jellybeans and have the child give her friends the same number of jelly beans out of the pile so that each had the same number. If the child couldn’t do that, the number in the pile was a prime number. Chloe got hired. Sharon would have made the cut too. The most senior person at lunch that day would not have made the cut.


hu-070615-2.pngInstead of sending an email, Chloe gave me a hand written card thanking me for imparting my wisdom and knowledge (?) and respecting her not only as an intern, but also as a professional. How could I not have treated her as a professional? Although I have been blogging since she was in grammar school, she knew more about social media and communications than I could ever know.


Her manager, Sharon, is a great mentor and an example of the type of managers that we have at Hitachi Data Systems who grow and develop our employees. Thanks to her and other managers like her, Hitachi Data Systems made the Fortune Inaugural list of 100 Best Workplaces for Millennials. We just made the cut at 100, but we were in good company with the likes of Google and Facebook. This was a little surprising to me, knowing Hitachi Data Systems to be part of a 100-year-old Japanese company, founded on Wa (Harmony), Makoto (Sincerity), and Kaitakusha Seishin (Innovation). I guess these principles still apply to our millenials.


Good luck to Chloe and all the millenials; the future is in your hands. Focus on Social Innovation and make this world a better place for our grandchildren and their children.