Tính hợp lí nếu có thể:
a) $\frac{3}{7}$ + $\frac{5}{13}$ + $\frac{4}{7}$ – $\frac{18}{13}$
b) 7,5 : (-$\frac{5}{3}$) + 2 $\frac{1}{2}$ :(-$\frac{5}{3}$)
c) $\frac{25}{23}$+ $\frac{7}{11}$- $\frac{2}{23}$- $\frac{1}{2}$+ $\frac{4}{11}$
Tính hợp lí nếu có thể:
a) $\frac{3}{7}$ + $\frac{5}{13}$ + $\frac{4}{7}$ – $\frac{18}{13}$
b) 7,5 : (-$\frac{5}{3}$) + 2 $\frac{1}{2}$ :(-$\frac{5}{3}$)
c) $\frac{25}{23}$+ $\frac{7}{11}$- $\frac{2}{23}$- $\frac{1}{2}$+ $\frac{4}{11}$
Đáp án:
\(\begin{array}{l}
a,0\\
b, – 6\\
c,\frac{3}{2}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a,\frac{3}{7} + \frac{5}{{13}} + \frac{4}{7} – \frac{{18}}{{13}}\\
= (\frac{3}{7} + \frac{4}{7}) + (\frac{5}{{13}} – \frac{{18}}{{13}})\\
= 1 – 1\\
= 0\\
b,7,5:\frac{{ – 5}}{3} + 2\frac{1}{2}:\frac{{ – 5}}{3}\\
= (7,5 + 2\frac{1}{2}):\frac{{ – 5}}{3}\\
= 10.\frac{{ – 3}}{5}\\
= – 6\\
c,\frac{{25}}{{23}} + \frac{7}{{11}} – \frac{2}{{23}} – \frac{1}{2} + \frac{4}{{11}}\\
= (\frac{{25}}{{23}} – \frac{2}{{23}}) + (\frac{7}{{11}} + \frac{4}{{11}}) – \frac{1}{2}\\
= 1 + 1 – \frac{1}{2}\\
= \frac{3}{2}
\end{array}\)
Đáp án:
Giải thích các bước giải:
a, 3/7+4/7+5/13-18/13=1-1=0
b, (7.5+5/2):-5/3=10:-5/3=-6
c, 25/23-2/23+7/11+4/11-1/2
=1+1-1/2=3/2=1,5