题目内容

计算,能简算的要用简算.
9-4.8÷6×0.5                
2.16÷[64.8-(51.3-2.7×3]
(1.4×0.3+2.46)÷1.8
(2.5÷2+2÷2.5)×0.4      
3.71+3.71×17.4-8.4×3.71       
1.2+8.8×1.25.
分析:(1)先算除法和乘法,再算减法;
(2)先算小括号内的乘法,再算小括号内的减法,然后算中括号的减法,最后算括号外的除法;
(3)先算括号内的乘法,再算括号内的加法,最后算括号外的除法;
(4)先算括号内的除法,再算括号内的加法,最后算括号外的乘法;
(5)运用乘法分配律简算;
(6)把8.8看作8+0.8,运用乘法分配律简算.
解答:解:(1)9-4.8÷6×0.5,
=9-0.4,
=8.6;

(2)2.16÷[64.8-(51.3-2.7×3],
=2.16÷[64.8-(51.3-8.1],
=2.16÷[64.8-43.2],
=2.16÷21.6,
=0.1;

(3)(1.4×0.3+2.46)÷1.8,
=(0.42+2.46)÷1.8,
=2.88÷1.8,
=1.6;

(4)(2.5÷2+2÷2.5)×0.4,
=(1.25+0.8)×0.4,
=2.05×0.4,
=0.82;

(5)3.71+3.71×17.4-8.4×3.71,
=(1+17.4-8.4)×3.71,
=10×3.71,
=37.1;

(6)1.2+8.8×1.25,
=1.2+(8+0.8)×1.25,
=1.2+8×1.25+0.8×1.25,
=1.2+10+1,
=12.2.
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定律进行简便计算.
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