Advanced Math/math


Dear Janet.  I write mystery novels.

I'm working on a project involving a safe, with a combination lock - 4 numbers, from0 to 99.

a character has the first number.  How many possible combnations would there be to get the next 3.

I know this would not be possible, but I want to explain to the reader just how difficult it would be.

Thank you,

Jerry Kennealy

There are 1000 possibilities for the last three digits. There happens to be a very good explanation of this very problem at, section 1.

One THOUSAND, not one hundred!

Advanced Math

All Answers

Answers by Expert:

Ask Experts


Janet Yang


I can answer questions in Algebra, Basic Math, Calculus, Differential Equations, Geometry, Number Theory, and Word Problems. I would not feel comfortable answering questions in Probability and Statistics or Topology because I have not studied these in depth.


I tutor students (fifth through twelfth grades) and am a Top Contributor on Yahoo!Answers with over 24,000 math solutions.

Co-author of An Outline of Scientific Writing: For Researchers With English as a Foreign Language

I have a Bachelor's degree in Applied Mathematics from the University of California at Berkeley.

Past/Present Clients
George White Elementary School. Homework Help program at the Ridgewood Public Library, Ridgewood, NJ. Individual students.

©2016 All rights reserved.