tính a) (1/5)+(2/5) = ...; b) 3*(1/2)=

* Hướng dẫn giải

a) $\frac{1}{5}+\frac{2}{5}=\frac{1+2}{5}=\frac{3}{5}$

b) $3\times \frac{1}{2}=\frac{3\times 1}{2}=\frac{3}{2}$

c) $1-\left(\frac{2}{3}+\frac{1}{6}\right)=1-\left(\frac{12}{18}+\frac{3}{18}\right)=1-\frac{15}{18}=\frac{3}{18}=\frac{1}{6}$

d) $1\frac{1}{5}÷1\frac{1}{2}=\frac{6}{5}÷\frac{3}{2}=\frac{12}{15}=\frac{4}{5}$

e) $\frac{3}{5}+\frac{2}{5}\times \frac{1}{6}=\frac{3}{5}+\frac{2}{30}=\frac{20}{30}=\frac{2}{3}$