2.5×1.25×32
=2.5×1.25×4×8
=2.54×8×1.25
=10×10
=100
（10＋0.1＋0.01）×39
=10×39+0.1×39+0.01×39
=390+3.9+0.39
=394.29
6.19×2.05＋79.5×0.619
=6.19×2.05＋7.95×6.19
=6.19×(2.05+7.95)
=61.9
0.86＋9.9×8.6
=8.6×0.1+9.9×8.6
=8.6×(0.1+9.9)
=86