From the problem, there are 10 red balls, 20 yellow balls and 40 orange balls.
The probability of selecting a red ball is the number of red balls divided by the total number of balls :
[tex]\begin{gathered} p=\frac{10}{10+20+40}=\frac{10}{70} \\ p=\frac{1}{7} \end{gathered}[/tex]The answer is 1/7
