GCSE Maths Practice: conditional-probability

Question 4 of 13

This question shows conditional probability by removing a subset. Focus only on remaining marbles.

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\( \begin{array}{l}\text{A box contains 4 white marbles, 5 black marbles, and 3 red marbles.} \\ \text{One marble is drawn randomly.} \\ \text{What is the probability the marble is red, given that it is not black?}\end{array} \)

Choose one option:

\( \frac{3}{7} \) \( \frac{3}{8} \) \( \frac{1}{4} \)

Count the remaining items after exclusion, then calculate probability.

When given a condition (not black), exclude black marbles from the total and recalc probability.