8 pens are to be selected from pens of 3 colours (pens of each colour being available any number of times), then total number of selections.

Options

A. 45
B. 90
C. 180
D. 28

Answer

A

Explanation

` ""^(3+8-1)C_(8) = ""^(10)C_(8) = (10.9)/(2) = 45`
Ans. [1]