分析:(1)把79看作80-1,根據(jù)乘法分配律簡(jiǎn)算;
(2)(3)根據(jù)乘法分配律簡(jiǎn)算;
(4)根據(jù)加法交換律、結(jié)合律簡(jiǎn)算;
(5)把12拆為4×3,再利用乘法結(jié)合律簡(jiǎn)算;
(6)根據(jù)加法交換律先加后減計(jì)算.
解答:解:(1)79×125,
=(80-1)×125,
=80×125-125,
=10000-125,
=9875;
(2)85×101-85,
=85×(101-1),
=85×100,
=8500;
(3)83×152-83×53+83,
=83×(152-53+1),
=83×100,
=8300;
(4)428+754+146+72,
=(428+72)+(754+146),
=500+900,
=1400;
(5)5.25×12×9,
=(5.25×4)×(3×9),
=21×27,
=567;
(6)
-+,
=
.
點(diǎn)評(píng):在運(yùn)用運(yùn)算定律進(jìn)行簡(jiǎn)便計(jì)算的時(shí)候,可先根據(jù)式中數(shù)據(jù)的特點(diǎn)及式中數(shù)據(jù)進(jìn)行拆分后再運(yùn)用運(yùn)算定律進(jìn)行計(jì)算.