怎樣算簡便就怎樣算.
25×137×40
4200-1934-1066
290×54+29×460
46×102+308.
解:(1)25×137×40,
=25×40×137,
=1000×137,
=137000;
(2)4200-1934-1066,
=4200-(1934+1066),
=4200-3000,
=1200;
(3)290×54+29×460,
=290×54+290×46,
=290×(54+46),
=290×100,
=29000;
(4)46×102+308,
=46×(100+2)+308,
=46×100+46×2+308,
=4600+92+308,
=4600+(92+308),
=4600+400,
=5000.
分析:(1)運(yùn)用乘法交換律簡算;
(2)根據(jù)連續(xù)減去兩個(gè)數(shù)等于減去這兩個(gè)數(shù)的和簡算;
(3)先根據(jù)積不變規(guī)律把加號(hào)左右變成含有相同的因數(shù),再運(yùn)用乘法分配律簡算;
(4)先把102化成100+2,再運(yùn)用乘法分配律簡算,然后再運(yùn)用加法結(jié)合律簡算.
點(diǎn)評:運(yùn)算定律是常用的簡便運(yùn)算的方法,要熟練掌握,靈活運(yùn)用.