题目内容
递等式计算,能简算的就简算 ①12.5×0.32×2.5 | ②3 |
③57× | ④0.75×99-% |
解:①12.5×0.32×2.5,
=12.5×8×0.4×2.5,
=(12.5×8)×(0.4×2.5),
=100×0.1,
=10;
②3-÷-,
=3-×-,
=3--,
=30-(+),
=3-2,
=1;
③57×,
=(56+1)×,
=56×+,
=55+,
=55;
④0.75×99-+2×75%,
=0.75×99-0.75+2×0.75,
=0.75×(99-1+2),
=0.75×100,
=75.
分析:①把0.32看作8×0.4,运用乘法结合律简算;
②先算除法和乘法,然后运用减法的性质简算;
③把57看作56+1,运用乘法分配律简算;
④把分数和百分数化为小数,运用乘法分配律简算.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
=12.5×8×0.4×2.5,
=(12.5×8)×(0.4×2.5),
=100×0.1,
=10;
②3-÷-,
=3-×-,
=3--,
=30-(+),
=3-2,
=1;
③57×,
=(56+1)×,
=56×+,
=55+,
=55;
④0.75×99-+2×75%,
=0.75×99-0.75+2×0.75,
=0.75×(99-1+2),
=0.75×100,
=75.
分析:①把0.32看作8×0.4,运用乘法结合律简算;
②先算除法和乘法,然后运用减法的性质简算;
③把57看作56+1,运用乘法分配律简算;
④把分数和百分数化为小数,运用乘法分配律简算.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
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