Solution
Sample space = {1, 2, 3, 4, 5, 6, 7, 8}
A = odd number = {1, 3, 5, 7}
count = 4
B = number less than 4 = {1, 2, 3}
count = 3
[tex]\begin{gathered} A\cap B=\lbrace1,3\rbrace \\ \\ P(A\cup B)=P(A)+P(B)-P(A\cap B) \\ \\ \Rightarrow P(A\cup B)=\frac{4}{8}+\frac{3}{8}-\frac{2}{8}=\frac{5}{8} \end{gathered}[/tex]The probability is 5/8