解:1.05+1.42÷(4.3+2.8),
=1.05+1.42÷7.1,
=1.05+0.2,
=1.25;
8.4×

+1.6×0.25,
=8.4×0.25+1.6×0.25,
=(8.4+1.6)×0.25,
=10×0.25,
=2.5;

-


+

,
=

-

+

,
=

-

+

,
=

,
=

;
(

)÷

,
=(1-

)×

×

,
=

,
=1

;
5-

-

,
=5-

-

,
=5-

-

,
=5-(

),
=5-

,
=

;
[

-(

)]÷

,
=[

-

]

,
=

×

,
=

.
分析:1.05+1.42÷(4.3+2.8),按運(yùn)算順序進(jìn)行計(jì)算,在運(yùn)算過程中,注意小數(shù)點(diǎn)的位置;
8.4×

+1.6×0.25,把

化成0.25,然后用乘法分配律的逆運(yùn)算簡(jiǎn)算;

-


+

,按運(yùn)算順序進(jìn)行計(jì)算,在運(yùn)算過程中注意通分;
(

)÷

,先算括號(hào)內(nèi)的,再算括號(hào)外的,在運(yùn)算過程中注意約分;
5-

-

,按運(yùn)算順序進(jìn)行計(jì)算,再算5-

-

時(shí),用減法的性質(zhì)簡(jiǎn)算,或算成5-

2;
[

-(

)]÷

,按運(yùn)算順序進(jìn)行計(jì)算,在運(yùn)算過程中注意約分.
點(diǎn)評(píng):此題重點(diǎn)考查學(xué)生對(duì)四則混合運(yùn)算順序的掌握情況,以及簡(jiǎn)算能力.