Concept:Probability of independent draws from three urns, adding all favorable cases.
Explanation:Each urn contains 5 balls, so every single draw has denominator 5.
We need exactly 1 black and 2 white balls in the selection.
There are three possible positions for the black ball: from urn 1, urn 2, or urn 3.
Case 1: Black from urn 1, white from urn 2, white from urn 3.
P=53​×53​×51​=1259​.
Case 2: White from urn 1, black from urn 2, white from urn 3.
P=52​×52​×51​=1254​.
Case 3: White from urn 1, white from urn 2, black from urn 3.
P=52​×53​×54​=12524​.
Required probability:
1259​+1254​+12524​=12537​.
Answer:12537​