1/10 : 1/4 + 1/5*1/2=

[tex] \frac{1}{10} : \frac{1}{4} + \frac{1}{5} \times \frac{1}{2} \\ = \frac{1}{10} \times 4 + \frac{1}{10} \\ = \frac{4+1}{10} = \frac{5}{10} = \frac{1}{2} [/tex]