Unformatted text preview: r).
I have seen some very good shortcuts for solving this question (and others like it). But I would like to offer
you a fast and foolproof method. My method is probability based and I call it "A probability approach for
solving counting problems" method.
Now let Y be the ... don't worry! No Y is needed, just wanted to sound smart! (And as you know every good
math/physics/finance paper starts with "let something be something")
So I would like to start with a simple problem, very simple problem:
How many integers from 1 to 100 including, has a units digit of 5?
This is a 350 level question; all you need to do is to list the integers that has 5 as the units digit, I call this
the basic method, meaning Count(5,15,25,35,45,55,65,75,85,95) = 10. The answer is (C).
Using the probability method we can see we have two places for digit in the integer XX and we need to fill in
the tens di...
View Full Document
- Fall '13
- Numerical digit, digit, 4-digit, 4 digits, probability method