例3 (陕西·咸阳)计算:
(1) $\displaystyle (-0.5)+3\ \frac{1}{4}+\left|-\frac{5}{3}\right|+2.75$;
(2) $\displaystyle -5\ \frac{5}{6}+(-3\ \frac{2}{3})+2\ \frac{3}{4}+(-1\ \frac{1}{2})$。
解:(1) $\displaystyle (-0.5)+3\ \frac{1}{4}+\left|-\frac{5}{3}\right|+2.75$
$\displaystyle =(-\frac{1}{2})+3\ \frac{1}{4}+\frac{5}{3}+2\ \frac{3}{4}$ ←——化简整理:将小数转化为分数,统一形式;去绝对值符号.
$\displaystyle =(-\frac{1}{2})+\frac{5}{3}+(3\ \frac{1}{4}+2\ \frac{3}{4})$ ←——将同分母的分数结合.
$\displaystyle =\frac{7}{6}+6$
$\displaystyle =7\ \frac{1}{6}$; ←——结果也可以写成$\displaystyle \frac{43}{6}$,但是不可以写成$\displaystyle 6\ \frac{7}{6}$.
(2) $\displaystyle -5\ \frac{5}{6}+(-3\ \frac{2}{3})+2\ \frac{3}{4}+(-1\ \frac{1}{2})$
$\displaystyle =[(-5)+(-\frac{5}{6})]+[(-3)+(-\frac{2}{3})]+(2+\frac{3}{4})+[(-1)+(-\frac{1}{2})]$ ←——遇到带分数时,可将其拆分为整数部分和分数部分,再利用加法交换律和结合律简便计算.
$\displaystyle =[(-5)+(-3)+2+(-1)]+[(-\frac{5}{6})+(-\frac{2}{3})+\frac{3}{4}+(-\frac{1}{2})]$ ←——
$\displaystyle =-7+[(-\frac{5}{6})+(-\frac{4}{6})+\frac{3}{4}+(-\frac{1}{2})]$ ←——多个分数相加时,可以分步通分.
$\displaystyle =-7+[-\frac{3}{2}+(-\frac{1}{2})+\frac{3}{4}]$
$\displaystyle =-8\ \frac{1}{4}$ . ←——结果也可以写成$\displaystyle -\frac{33}{4}$.
(1) $\displaystyle (-0.5)+3\ \frac{1}{4}+\left|-\frac{5}{3}\right|+2.75$;
(2) $\displaystyle -5\ \frac{5}{6}+(-3\ \frac{2}{3})+2\ \frac{3}{4}+(-1\ \frac{1}{2})$。
解:(1) $\displaystyle (-0.5)+3\ \frac{1}{4}+\left|-\frac{5}{3}\right|+2.75$
$\displaystyle =(-\frac{1}{2})+3\ \frac{1}{4}+\frac{5}{3}+2\ \frac{3}{4}$ ←——化简整理:将小数转化为分数,统一形式;去绝对值符号.
$\displaystyle =(-\frac{1}{2})+\frac{5}{3}+(3\ \frac{1}{4}+2\ \frac{3}{4})$ ←——将同分母的分数结合.
$\displaystyle =\frac{7}{6}+6$
$\displaystyle =7\ \frac{1}{6}$; ←——结果也可以写成$\displaystyle \frac{43}{6}$,但是不可以写成$\displaystyle 6\ \frac{7}{6}$.
(2) $\displaystyle -5\ \frac{5}{6}+(-3\ \frac{2}{3})+2\ \frac{3}{4}+(-1\ \frac{1}{2})$
$\displaystyle =[(-5)+(-\frac{5}{6})]+[(-3)+(-\frac{2}{3})]+(2+\frac{3}{4})+[(-1)+(-\frac{1}{2})]$ ←——遇到带分数时,可将其拆分为整数部分和分数部分,再利用加法交换律和结合律简便计算.
$\displaystyle =[(-5)+(-3)+2+(-1)]+[(-\frac{5}{6})+(-\frac{2}{3})+\frac{3}{4}+(-\frac{1}{2})]$ ←——
$\displaystyle =-7+[(-\frac{5}{6})+(-\frac{4}{6})+\frac{3}{4}+(-\frac{1}{2})]$ ←——多个分数相加时,可以分步通分.
$\displaystyle =-7+[-\frac{3}{2}+(-\frac{1}{2})+\frac{3}{4}]$
$\displaystyle =-8\ \frac{1}{4}$ . ←——结果也可以写成$\displaystyle -\frac{33}{4}$.
答案
解:
(1) 原式$=-\frac{1}{2}+3\frac{1}{4}+\frac{5}{3}+2\frac{3}{4}$
$=(-\frac{1}{2}+\frac{5}{3})+(3\frac{1}{4}+2\frac{3}{4})$
$=\frac{7}{6}+6$
$=7\frac{1}{6}$
(2) 原式$=[(-5)+(-\frac{5}{6})]+[(-3)+(-\frac{2}{3})]+(2+\frac{3}{4})+[(-1)+(-\frac{1}{2})]$
$=[(-5)+(-3)+2+(-1)]+[(-\frac{5}{6})+(-\frac{2}{3})+\frac{3}{4}+(-\frac{1}{2})]$
$=-7+[(-\frac{5}{6})+(-\frac{4}{6})+\frac{3}{4}+(-\frac{1}{2})]$
$=-7+[-\frac{3}{2}+(-\frac{1}{2})+\frac{3}{4}]$
$=-7+(-2+\frac{3}{4})$
$=-8\frac{1}{4}$
(1) 原式$=-\frac{1}{2}+3\frac{1}{4}+\frac{5}{3}+2\frac{3}{4}$
$=(-\frac{1}{2}+\frac{5}{3})+(3\frac{1}{4}+2\frac{3}{4})$
$=\frac{7}{6}+6$
$=7\frac{1}{6}$
(2) 原式$=[(-5)+(-\frac{5}{6})]+[(-3)+(-\frac{2}{3})]+(2+\frac{3}{4})+[(-1)+(-\frac{1}{2})]$
$=[(-5)+(-3)+2+(-1)]+[(-\frac{5}{6})+(-\frac{2}{3})+\frac{3}{4}+(-\frac{1}{2})]$
$=-7+[(-\frac{5}{6})+(-\frac{4}{6})+\frac{3}{4}+(-\frac{1}{2})]$
$=-7+[-\frac{3}{2}+(-\frac{1}{2})+\frac{3}{4}]$
$=-7+(-2+\frac{3}{4})$
$=-8\frac{1}{4}$
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