A box has 6 black, 4 red, 2 white and 3 blue shirts. When 2 shirts are picked randomly, what is the probability that either both are white or both are blue?

Answer: Option A

Both white or both blue
Total shirts = 15
There are 2 white and 3 blue shirts
Probability for 2 white shirts $$=\frac{2}{15}\times \frac{1}{14}=\frac{1}{105}$$
Probability for 2 blue shirts $$=\frac{3}{15}\times \frac{2}{14}=\frac{1}{35}$$
Total Probability $$=\frac{1}{105}+\frac{1}{35}=\frac{4}{105}$$