用简便方法计算(写出简算过程)
①(++)×12??????????????????
②18.93-6-3
③163×-0.75×62-75%??????????????
④7÷+1×2.
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解:①(++)×12,
=×12+×12+×12,
=4+3+2,
=9;
②18.93-6-3,
=18.93-(6+3),
=18.93-10,
=8.93;
③163×-0.75×62-75%,
=163×0.75-0.75×62-0.75,
=(163-62-1)×0.75,
=100×0.75,
=75;
④7÷+1×2,
=7×+×2,
=(7+2)×,
=10×,
=.
解析分析:①根据数字特点,运用乘法分配律的逆运算简算;②运用减法的性质简算;③把分数、百分数化为小数,运用乘法分配律的逆运算简算;④把除法改为乘法,运用乘法分配律的逆运算简算.
点评:此题主要考查了四则混合运算的简算,应根据数字特点,运用恰当的运算定律和性质进行简算.