分析:(1)根據(jù)乘法分配律進(jìn)行計(jì)算;
(2)先算小括號里面的減法和加法,再算乘法,最后算除法;
(3)根據(jù)加法交換律和結(jié)合律進(jìn)行計(jì)算;
(4)根據(jù)等式的性質(zhì)進(jìn)行解答.
解答:解:
(1)5.35×0.25+2.65×
,
=5.35×0.25+2.65×0.25,
=(5.35+2.65)×0.25,
=8×0.25,
=2;
(2)
[(1-)(1-)(1-)]÷(0.1+0.2+0.3),
=[
×
×
]÷0.6,
=
÷0.6,
=
;
(3)9
+99
+999+3×
,
=9.9+99.9+999.9+(0.1+0.1+0.1),
=(9.9+0.1)+(99.9+0.1)+(999.9+0.1),
=10+100+1000,
=1110;
(4)3x-0.8×75%=2.1,
解:3x-0.6=2.1,
3x-0.6+0.6=2.1+0.6,
3x=2.7,
3x÷3=2.7÷3,
x=0.9.
點(diǎn)評:考查了運(yùn)算定律與簡便運(yùn)算,四則混合運(yùn)算.注意運(yùn)算順序和運(yùn)算法則,靈活運(yùn)用所學(xué)的運(yùn)算律簡便計(jì)算.