题目内容

递等式计算,能简算的就简算.
(1)3.7+6.3×0.5
(2)21.6÷3×(20-19.8)
(3)2.5×2.9×4×2
(4)16.53-3.57-6.43
(5)5.28×9.8+0.2×5.28
(6)28-2×9.5+2.8
(7)(10-9.2)×(2.6-2.1)÷5
(8)1.5×[(3.6-0.36÷0.6)-5].
分析:(1)先算乘法,再算加法;
(2)先算除法和括号内的,最后算乘法;
(3)运用乘法交换律与结合律简算;
(4)运用减法的性质简算;
(5)运用乘法分配律简算;
(6)先算乘法,再从左往右依次运算;
(7)两个括号同时计算,再从左往右依次运算;
(8)先算小括号内的除法,再算小括号内的减法,然后算中括号内的,最后算括号外的.
解答:解:(1)3.7+6.3×0.5,
=3.7+3.15,
=6.85;

(2)21.6÷3×(20-19.8),
=7.2×0.2,
=1.44;

(3)2.5×2.9×4×2,
=(2.5×4)×(2.9×2),
=10×5.8,
=58;

(4)16.53-3.57-6.43,
=16.53-(3.57+6.43),
=16.53-10,
=6.53;

(5)5.28×9.8+0.2×5.28,
=(9.8+0.2)×5.28,
=10×5.28,
=52.8;

(6)28-2×9.5+2.8,
=28-19+2.8,
=9+2.8,
=11.8;

(7)(10-9.2)×(2.6-2.1)÷5,
=0.8×0.5÷5,
=0.4÷5,
=0.08;

(8)1.5×[(3.6-0.36÷0.6)-5],
=1.5×[(3.6-0.6)-5],
=1.5×[3-5],
=1.5×(-2),
=-3.
点评:此题考查了小数的四则混合运算,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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