Answer:
The probability that Petra picks two black marbles, without replacing the first one is 7/15 or 46.7%.
Step-by-step explanation:
Let's recall the formula of the probability:
Probability = Number of favorable outcomes/Total number of possible outcomes,
therefore, the probability of picking a first black marble is:
P = 7/10
now, let's find out the probability for picking a second black marble:
P = 6/9
It's different than the first one because Petra did not replace the first one.
Now, the probability that both are black is:
P = 7/10 * 6/9
P = 42/90 = 7/15
The probability that Petra picks two black marbles, without replacing the first one is 7/15 or 46.7%
