Giải bài 1.7 trang 13

Đề bài

Tính:

a) $\frac{-6}{18}+\frac{18}{27}$;

b) $2,5-(-\frac{6}{9})$;

c) $-0,32.(-0,875)$;

d) $(-5):2\frac{1}{5}$

Lời giải chi tiết

a) $\frac{-6}{18}+\frac{18}{27}$

$=\frac{-1}{3}+\frac{2}{3}=\frac{1}{3}$

b) $2,5-(-\frac{6}{9})$

$=\frac{25}{10}+\frac{6}{9}=\frac{5}{2}+\frac{2}{3}=\frac{15}{6}+\frac{4}{6}=\frac{19}{6}$

c) $-0,32.(-0,875)$

$=\frac{-32}{100}.(-\frac{875}{1000})=\frac{-8}{25}.\left(\frac{-7}{8}\right)=\frac{8}{25}.\frac{7}{8}=\frac{7}{25}$

d) $(-5):2\frac{1}{5}$

$=(-5):\frac{11}{5}=(-5).\frac{5}{11}=\frac{-25}{11}$