用递等式计算．
21.5÷[（6.07+2.53）]；     （2.25+27.75÷1.5）×1.6．

列竖式计算．

0.37×0.4=	1.06×25=	27×0.43=	0.6×0.39=
1.7×0.86=	1.8×2.3=	2.07×53=	0.015×2.4=
3.4×1.6=	1.08×5.2=	1.25×3.6=	3.75×0.24=