4150÷1625
=4150×4÷（1625×4）
=16600÷6500
=166/65
20.05×39+200.5×4.1+4.4×10.005
=20×39+200×4.1+4.4×10+0.05×39+0.5×4.1+4.4×0.005
=780+820+44+1.95+2.05+0.022
=1644+4.022
=1648.022
（2005+2006+2007+2008+2009+2010+2011）÷2008
=2008×7÷2008
=7