用簡(jiǎn)便方法計(jì)算:
1.29+3.7+0.71+6.3 528×78+472×78 46.5×99+46.5
125×89×8 12.37-5.32-4.68 12.5×(0.8+8)
解:①1.29+3.7+0.71+6.3,
=(1.29+0.71)+(3.7+6.3),
=2+10,
=12;
②528×78+472×78,
=(528+472)×78,
=1000×78,
=78000;
③46.5×99+46.5,
=(99+1)×46.5,
=100×46.5,
=4650;
④125×89×8,
=125×8×89,
=1000×89,
=89000;
⑤12.37-5.32-4.68,
=12.37-(5.32+4.68),
=12.37-10,
=2.37;
⑥12.5×(0.8+8),
=12.5×0.8+12.5×8,
=10+100,
=110.
分析:①用加法結(jié)合律簡(jiǎn)算,②③⑥用乘法分配律簡(jiǎn)算,④用乘法交換律簡(jiǎn)算,⑤根據(jù)減去兩個(gè)數(shù)等于減去這兩個(gè)數(shù)的和來簡(jiǎn)算.
點(diǎn)評(píng):記住常用的簡(jiǎn)算方法,并靈活運(yùn)用.