In a box, there are 5 black pens, 3 white pens and 4 red pens. In how many ways can 2 black pens, 2 white pens and 2 red pens can be chosen?

Number of ways of choosing 2 black pens from 5 black pens in ⁵C₂ ways.
Number of ways of choosing 2 white pens from 3 white pens in ³C₂ ways.
Number of ways of choosing 2 red pens from 4 red pens in ⁴C₂ ways.
By the Counting Principle, 2 black pens, 2 white pens, and 2 red pens can be chosen in 10 x 3 x 6 = 180 ways