分析:(1)利用乘法交換律和結(jié)合律先計(jì)算0.8×1.25,再與3.9相乘;
(2)利用乘法分配律的逆運(yùn)算進(jìn)行簡便計(jì)算;
(3)把9.9寫成10-0.1,再利用乘法分配律計(jì)算即可解答;
(4)根據(jù)連減的性質(zhì):a-b-c=a-(c+b)進(jìn)行簡便計(jì)算即可解答;
(5)把3.2寫成0.4×8,再把2.5和0.4相乘,8和12.5相乘,再把所得的積相乘即可;
(6)此題沒有簡便計(jì)算的方法,按照運(yùn)算順序,先算乘法,再算加法,計(jì)算即可.
解答:解:(1)0.8×3.9×1.25
=0.8×1.25×3.9
=1×3.9
=3.9
(2)4.87×2.34+4.87×7.66
=4.87×(2.34+7.66)
=4.87×10
=48.7
(3)0.49×9.9
=0.49×(10-0.1)
=0.49×10-0.49×0.1
=4.9-0.049
=4.851
(4)60.8-7.18-12.82
=60.8-(7.18+12.82)
=60.8-20
=40.8
(5)2.5×3.2×12.5
=2.5×(0.4×8)×12.5
=(2.5×0.4)×(8×12.5)
=1×100
=100
(6)3.95×7.6+2.4
=30.02+2.4
=32.42.
點(diǎn)評:完成本題要注意分析式中數(shù)據(jù),運(yùn)用合適的簡便方法計(jì)算.