3.8*41-0.38
=3.8*4.1-3.8*0.1
=3.8*(4.1-0.1)
=3.8*4
=(4-0.2)*4
=16-0.8
=15.2错了，41怎麽变4.1了？3.8*41-0.38=3.8*(40+1)-0.38=152+3.8-0.38=155+0.8-0.38=155+0.42=155.42