Math problems May 18 2012

Problem #1

Calculate 2004 - 2003 + 2002 - 2001 + 2000 - 1999 + ... + 2 - 1

Problem # 2
To print page numbers in a book we need 204 digits. How many pages in this book if we start with page 1?
Problem #3
In the appartments A, B, and C there are 3 cats: white, black and red. In appartments A and B there is not black cat. White cat is not in appartment A? Where is each cat?
Problem # 4
Cut rectangular in 3 triangulars in a such way so that only one of them has right angle.
Problem #5
From the number 12345678910111213…5657585960 cut 100 digits so the resulting number is largest one.
Problem #6
There are two sand watches: for 3 and 7 minutes. An egg can be boiled within 11 minutes. How to measure it using these sand watches?