题目内容

3.计算题
75+25×105-1344÷42
58.8÷(0.6×0.7)+80×0.125
(0.5+4.2×$\frac{5}{6}$)÷(0.5×4.2×$\frac{5}{6}$)
[14$\frac{1}{6}$-(3$\frac{3}{5}$+2$\frac{2}{3}$)×1$\frac{7}{8}$]÷7$\frac{1}{4}$
[(1$\frac{2}{25}$-0.28)×$\frac{5}{13}$+1÷(0.75+$\frac{1}{3}$)]×1$\frac{19}{20}$.

分析 (1)先算除法和除法,再算加法,最后算减法;
(2)先算乘法,再算除法,最后算加法;
(3)先算乘法,再算加法,最后算除法;
(4)先算加法,再算乘法,再算减法,最后算除法;
(5)先算小括号里面的减法和加法,再算中括号里面的乘法和除法,再算中括号里面的加法,最后算括号外面的乘法.

解答 解:(1)75+25×105-1344÷42
=75+2625-32
=2700-32
=2668;

(2)58.8÷(0.6×0.7)+80×0.125
=58.8÷0.42+10
=140+10
=150;

(3)(0.5+4.2×$\frac{5}{6}$)÷(0.5×4.2×$\frac{5}{6}$)
=(0.5+3.5)÷(2.1×$\frac{5}{6}$)
=(0.5+3.5)÷1.75
=4÷1.75
=$\frac{16}{7}$;

(4)[14$\frac{1}{6}$-(3$\frac{3}{5}$+2$\frac{2}{3}$)×1$\frac{7}{8}$]÷7$\frac{1}{4}$
=[14$\frac{1}{6}$-6$\frac{4}{15}$×1$\frac{7}{8}$]÷7$\frac{1}{4}$
=[14$\frac{1}{6}$-11$\frac{3}{4}$]÷7$\frac{1}{4}$
=2$\frac{5}{12}$÷7$\frac{1}{4}$
=$\frac{1}{3}$;

(5)[(1$\frac{2}{25}$-0.28)×$\frac{5}{13}$+1÷(0.75+$\frac{1}{3}$)]×1$\frac{19}{20}$
=[0.8×$\frac{5}{13}$+1÷$\frac{13}{12}$]×1$\frac{19}{20}$
=[$\frac{4}{13}$+$\frac{12}{13}$]×1$\frac{19}{20}$
=$\frac{16}{13}$×1$\frac{19}{20}$
=$\frac{12}{5}$.

点评 考查了整数、分数和小数四则混合运算,注意运算顺序和运算法则,然后再进一步计算.

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