Problem Solving Skills for Mathcounts Competitions

Book Store => Bookstore => Twenty Files Questions => Topic started by: lunastar on January 13, 2011, 07:37:24 PM

Title: I don't understand part of a formula
Post by: lunastar on January 13, 2011, 07:37:24 PM

In chapter 6, there's a bracket-parenthesis thing and I don't understand how you use it. Can you explain?

Title: Re: I don't understand part of a formula
Post by: yongcheng3315 on January 13, 2011, 08:02:28 PM

Are you talking about the notation for combinations of n things taken r at a time? If so, that is the same as C(m,n), or nCr .

Title: Re: I don't understand part of a formula
Post by: lunastar on January 14, 2011, 08:00:00 PM

It was for the number of ways to walk from one corner to another corner of an m by n grid. It's used in several formulas after that too, like Newton's Little Formula.
Also in Pythagorean Triples, how do you find the total of factors/odd factors in x^2?

Title: Re: I don't understand part of a formula
Post by: yongcheng3315 on January 16, 2011, 07:03:21 PM

Check out here:

http://www.mymathcounts.com/Forum/index.php?topic=250.0

How to find the number of factors? See "twenty more problem solving skills" chapter 2 divisor and divisibility.

Title: Re: I don't understand part of a formula
Post by: lunastar on January 17, 2011, 07:53:20 PM

Thanks for the help!