Question

2．递等式计算，能简便的要简便：
0.125×1.6×7.5
2.56×62.1+2.56×37+25.6×0.1
（0.18+0.18+0.18+0.18）×2.5        
（6.78+6.78÷6.78-6.78）×6.78．

Answer 1

分析 ①先把1.6分解成8×0.2，再运用乘法交换律和结合律简算，
②先把25.6×0.1变成2.56×1，再用乘法分配律简算，
③先把0.18+0.18+0.18+0.18变成0.18×4，再用乘法交换律简算，
④先算小括号的除法，再用加法交换律计算减法加法，最后算乘法．

解答 解：①0.125×1.6×7.5
=0.125×（8×0.2）×7.5
=（0.125×8）×（0.2×7.5）
=1×1.5
=1.5

②2.56×62.1+2.56×37+25.6×0.1
=2.56×62.1+2.56×37+2.56×1
=2.56×（62.1+37+1）
=2.56×100.1
=2.56×（100+0.1）
=2.56×100+2.56×0.1
=256+0.256
=256.256

③（0.18+0.18+0.18+0.18）×2.5  
=（0.18×4）×2.5
=0.18×（4×2.5）
=0.18×10
=1.8

④（6.78+6.78÷6.78-6.78）×6.78
=（6.78+1-6.78）×6.78
=（6.78-6.78+1）×6.78
=1×6.78
=6.78

点评 此题考查小数四则混合运算顺序和灵活运用运算定律，分析数据找到正确的计算方法．