What is the simple calculation process from 2011 * 20022002 to 2002 * 20012001

What is the simple calculation process from 2011 * 20022002 to 2002 * 20012001

2011*20022002-2002*20012001
=2011*2002*10001-2001*2002*10001
=（2011-2001）*2002*10001
=10*20022002
=200220020

Calculation method of 2009 × 20012001-2001 × 20092009

2009×20012001-2001×20092009
=2009*2001*10001-2001*2009*10001
=0

2009 * 20012001-2001 * 20092009 = 2009 * 2001 * 10001-2001 * 2009 * 10001 = how did 10001 come from?

2001*10001=20012001

How to divide 20102010 by 20112011
Come on, it's tonight

20102010=2010×10001
20112011=2011×10001
∴20102010 ÷ 20112011 = (2010×10001) ÷ (2011×10001) = 2010/2011