：6.23x6.5+（2.15-1.8）x62.3
=6.23x6.5+（2.15-1.8）x6.23x10=
=6.23x[6.5+（2.15-1.8）x10]
=6.23x[6.5+3.5]=62.3
第二题：3.4x1.25x0.28=3.4x1.25x0.4x0.7
=3.4x0.5x0.7
第三题：3.6x2.8+9x7.2+2.8x5.4
=(3.6+5.4)x2.8+9x7.2==9x2.8+9x7.2==9x(2.8+7.2)=90
第四题：0.2222x1.8+0.1111x6.4
=0.1111x2x1.8+0.1111x6.4
=0.1111x(2x1.8+6.4)
=0.1111x10
=1.111
第五题：0.8x（1.25+2.5)x0.4
=0.8x1.25x0.4+0.8x2.5x0.4
=1x0.4+0.8x1=1.2