Let 5 red pens be R1 , R2 , R3 , R4 , R5 . 8 blue pens be B1 , B2 , B3 , B4 , B5 , B6 , B7 , B8 . and 3 green pens be G1 , G2 , G3 .
Sample space,
S = {R1 , R2 , R3 , R4 , R5, B1 , B2 , B3 , B4 , B5 , B6 , B7 , B8, G1 , G2 , G3 }
∴ n(S) = 16
Let A be the event that Rutuja picks a blue pen.
∴ A = {B1 , B2 , B3 , B4 , B5 , B6 , B7 , B8}
∴ n(A) = 8
∴ P(A) = \(\frac{n(A)}{n(S)}\)= 8/16
∴ P(A) = 1/2
∴ The probability that Rutuja picks a blue pen is 1/2 .