There are two urns.

Question

There are two urns. Urn A has 3 distinct red balls and urn B has 9 distinct blue balls. From each urn two balls are taken out at random and then transferred to the other. The number of ways in which this can be done is:

Accepted Answer

Choose 2 balls from urn A: $\binom32=3$; choose 2 balls from urn B: $\binom92=36$.

$$\text{Total} = 3\times36 = 108$$

Solutions · 1