解:(1)12.75+34+7.25,
=(12.75+7.25)+34,
=20+34,
=54;
(2)101×25,
=(100+1)×25,
=100×25+25,
=2500+25,
=2525;
(3)0.8+99×0.8,
=(1+99)×0.8,
=100×0.8,
=80;
(4)8×33×1.25,
=(8×1.25)×33,
=10×33,
=330;
(5)480÷5÷2,
=480÷(5×2),
=480÷10,
=48;
(6)(4.2+4.2÷2.1)÷0.2,
=(4.2+2)÷0.2,
=6.2÷0.2,
=31;
(7)[32-(1.65-1.65)]÷1.6,
=[32-0]÷1.6,
=32÷1.6,
=20.
分析:(1)運用加法交換律簡算;
(2)把101看作100+1,運用乘法分配律簡算;
(3)運用乘法分配律簡算;
(4)運用乘法交換律與結(jié)合律簡算;
(5)運用除法的性質(zhì)簡算;
(6)先算括號內(nèi)的除法,再算括號內(nèi)的加法,最后算括號外的除法;
(7)先算小括號內(nèi)的,再算中括號內(nèi)的,最后算括號外的.
點評:此題考查了整數(shù)、小數(shù)的四則混合運算,注意運算順序和運算法則,靈活運用所學(xué)的運算律簡便計算.