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Google Billboard

In July of 2004 a mysterious billboard appeared in Silicon Valley. All it said was

 {first ten digit prime found in consecutive digits of e}.com

At the same time, an identical banner appeared in the Harvard Square subway station in Boston. No indication was given about the significance of the signs, but people who correctly discovered the ten digit prime and visited the website were given a subsequent puzzle. If they completed that problem correctly they received a fawning message encouraging them and their "Big, Magnificent Brain" to apply for a job at Google Labs.

Suggested steps to complete the assignment

  1. Go to, log in, and do the isPrime problem
  2. You may find slides 4 - 42 of the APJavaStrings slide presentation helpful
  3. Now you are ready to start the project. Fork and clone down this repository
  4. In setup() use the two argument version of substring() to pull out ten consecutive digits of e at a time. Convert them to doubles with Double.parseDouble(). Here's an example:
    String digits = e.substring(2,12);
    double dNum = Double.parseDouble(digits);
    System.out.println(dNum); //displays 7.182818284E9
    Note that by default, Java displays doubles in exponential form. 7.182818284E9 is 7.182818284 x 10^9.
  5. Finish the isPrime() to test if a number is prime.
  6. Add a loop to setup() that moves through the digits of e until it finds the first 10 digit prime.
  7. Add commit and push your finished program to your github account.
  8. There is no website for this assignment, so instead of the GitHub pages URL, submit the url of your GitHub repository to Google classroom. The url of your repository will have the form your github username /GoogleBillboard
  9. If you have extra time you may want to see if you can solve the second puzzle.


An AP Computer Science A programming assignment for Mr. Simon's APCSA course at Lowell High School, San Francisco, USA




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