题目内容
3.脱式计算(注意使计算简便)3.6÷15+2.5×1.4
1.7×0.21+1.7×0.79
0.25+1.4+0.75-0.4
(4-0.4)×2.5.
分析 (1)先算除法和乘法,再算加法;
(2)、(4)根据乘法分配律进行简算;
(3)根据加法交换律和结合律进行简算.
解答 解:(1)3.6÷15+2.5×1.4
=0.24+3.5
=3.74;
(2)1.7×0.21+1.7×0.79
=1.7×(0.21+0.79)
=1.7×1
=1.7;
(3)0.25+1.4+0.75-0.4
=(0.25+0.75)+(1.4-0.4)
=1+1
=2;
(4)(4-0.4)×2.5
=4×2.5-0.4×2.5
=10-1
=9.
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定律简便计算.
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