题目内容

14.脱式计算.(能简算的要简算)
0.125×3.2×2.50.8×6.3-0.8×3.3204÷(3.4×0.5)7.85×0.25÷4
4.5+13.4×0.5-9.92.81+4×15.2×.54.58×99+1.58(20-0.8×9)×5.7.

分析 (1)把3.2化成8×0.4,再运用乘法的结合律进行简算即可;
(2)根据乘法分配律的逆定律计算;
(3)先算括号内的成发,再算括号外的除法;
(4)从左往右依次计算;
(5)先算乘法,然后从左往右依次计算;
(6)运用乘法交换律和结合律简算;
(7)运用乘法分配律简算;
(8)先算括号内的成发,再算括号内的减法,最后算括号外的乘法.

解答 解:(1)0.125×3.2×2.5
=0.125×8×0.4×2.5
=(0.125×8)×(0.4×2.5)
=1×1
=1

(2)0.8×6.3-0.8×3.3
=0.8×(6.3-3.3)
=0.8×3
=2.4

(3)204÷(3.4×0.5)
=204÷1.7
=120

(4)7.85×0.25÷4
=1.9625÷4
=0.490625

(5)4.5+13.4×0.5-9.9
=4.5+6.7-9.9
=11.2-9.9
=1.3

(6)2.81+4×15.2×5
=2.81+(4×5)×15.2
=2.81+20×15.2
=2.81+304
=306.81

(7)4.58×99+1.58
=4.58×(100-1)+1.58
=458-4.58+1.58
=458-(4.58-1.58)
=458-3
=455

(8)(20-0.8×9)×5.7
=(20-7.2)×5.7
=12.8×5.7
=72.96

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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