54.9×0.38=20.8624.05+37.85=41.91.25×0.8×0.7=1×0.7=0.79.8×25=2456.1×3.6+3.6×3.9=（6.1+3.9）×3.6=10×3.6=362.96×40=118.4
解:4.05+37.85=(4+0.05)+(37+0.85)=(4+37)+(0.05+0.85)=41+0.9=41.9
