Simple calculation: 2000 times 1949

Simple calculation: 2000 times 1949

2000 times 1949
=(10-1/2001)*1949
=19490-1949/2001
=19489-52 / 2001

How to calculate 25 * 42

According to the law of multiplicative distribution, 42 can be divided into (40 + 2)
25*（40+2）
=25*40+25*2
=1000+50
=1050

1、4.26-0.15-0.15-0.15-0.15
2、6.75×2.4+7.6×6.75

1、4.26-0.15-0.15-0.15-0.15
=4.26-0.15x4
=4.26-0.6
=3.66
2、6.75×2.4+7.6×6.75
=6.75x（2.4+7.6）
=6.75x10
=67.5
Don't understand can ask, help please adopt, thank you!

Out of form calculation 100 (with answers)

It seems that I asked this question in 2012