total cards = 16
total number of ways of choosing two cards randomly = 16C2 where nCr = n!/r!
number of ways of choosing blue card = 4C1
number of ways of choosing yellow card = 2C1
Probability = favorable outcomes / total outcomes
probability of choosing blue card and yellow card = 4C1 * 2C1 /16C1
= 1/15 = 0.066