简便计算 489*101-4 89 33*1.03 5.6*9+56 0.98*54 28*45+30*13

489*101-489
=489*(101-1)
=489*100
=48900
33*1.03
=33*(1+0.03)
=33+0.99
=33.99
5.6*9+56
=5.6*(10-1)+56
=56-5.6+56
=50.4+56
=106.4
0.98*54
=(1-0.02)*54
=54-0.02*(50+4)
=54-0.02*50-0.02*4
=54-1-0.08
=52.92
28*45+30*13
=15*28*3+15*2*13
=15*(84+26)
=15*110
=15*(100+10)
=1500+150
=1650