分析:(1)(3)利用乘法分配律進(jìn)行運(yùn)算;(2)(5)用乘法的交換律和結(jié)合律進(jìn)行計(jì)算;(4)(6)按照小數(shù)的四則混合運(yùn)算的運(yùn)算順序進(jìn)行計(jì)算.
解答:解:(1)99×4.2+4.2
=4.2×(99+1),
=4.2×100,
=420;
(2)0.25×1.25×3.2
=0.25×1.25×(4×0.8),
=0.25×4×(1.25×0.8),
=1×1,
=1;
(3)6.4×14+15×6.4+6.4
=6.4×(14+15+1),
=6.4×30,
=192;
(4)(1.3+1.3×0.125×8)÷(80-77.4)
=(1.3+1.3×1)÷2.6,
=2.6÷2.6,
=1;
(5)4×(25+2.5+0.25)÷111
=(4×25+4×2.5+4×0.25)÷111,
=(100+10+1)÷111,
=111÷111,
=1;
(6)6.25÷[(17.2-3.6×4.5)÷0.32]
=6.25÷[(17.2-16.2)÷0.32],
=6.25÷(1÷0.32),
=6.25÷3.125,
=2.
點(diǎn)評(píng):考查我們可以利用乘法結(jié)合律、分配律和交換律進(jìn)行簡(jiǎn)便運(yùn)算,不能簡(jiǎn)便運(yùn)算的我們就按小數(shù)四規(guī)混合運(yùn)算的順序來(lái)計(jì)算.