Aditya has a total of 18 red and blue marbles in two bags (each bag has marbles of both colors). A
marble is randomly drawn from the first bag followed by another randomly drawn from the
second bag, the probability of both being red is 5/16. What is the probability of both marbles being blue?

Probability of both marbles being red = Probability of red from 1st * probability of red from 2nd

= $$\frac{5}{16}$$

$$\because$$ Each bag has marbles of both colors and probability cannot be greater than 1

=> $$\frac{5}{16} = \frac{5}{8} \times \frac{1}{2}$$ 

where, probability of red marbles from 1st bag = $$\frac{5}{8}$$

=> Probability of blue marbles from 1st bag = $$1 - \frac{5}{8} = \frac{3}{8}$$

Similarly, Probability of red marbles from 1st bag = $$\frac{1}{2}$$

=> Probability of blue marbles from 2nd bag = $$1 - \frac{1}{2} = \frac{1}{2}$$

$$\therefore$$ Probability of both blue marbles = $$\frac{3}{8} \times \frac{1}{2}$$

= $$\frac{3}{16}$$