Answer
$\frac{7}{30}$
Work Step by Step
As the urn contains 7 black marbles and total 30 marbles, the probability of getting a black marble is $\frac{7}{30}$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.