The probability that an event A occurs (P(A)) is:
To solve this question, follow the steps below.
Step 01: Calculate the probability the first marble is red.
Number of favorable outcomes = 5 (5 red marbles).
Number of total outcomes = 10 (10 marbles).
Then, P(red₁):
Step 02: Calculate the probability the second ball is also red.
Now, let's assume that 1 red ball was removed. Then,
Number of favorable outcomes = 4 (4 red marbles remained).
Number of total outcomes = 9 (number of total marbles remained).
Then, P(red₂):
Step 03: Calculate the probability the first and the second marbles are red.
The probability both marbles are red is the product of both probabilities.
And dividing the numerator and denominator by 4:
Answer: The probability that both marbles he chooses are red is 2/9.